WOGONT  AND  THE  FUNDAMENTAL  PROBLEMS  OF  GEULWtY 


IE  GASES  IN  ROCKS 


BOLLIN  THOMAS  CHx\MBEBLIN 


!  [INGTON,  D.  C, 
KfcAENEeiE  INSTITUTION  OF  W 


CONTRIBUTIONS  TO  COSMOGONY  AND  THE  FUNDAMENTAL  PROBLEMS  OF  GEOLOGY 


THE  GASES  IN  ROCKS 


BY 


EOLLIN  THOMAS  CHAMBEELIN 


WASHINGTON,  D.  C. 

PUBLISHED  BY  THE  CARNEGIE  INSTITUTION  OF  WASHINGTON 
1908 


SI  I 


CAKNEGIE  INSTITUTION  OF  WASHINGTON 
PUBLICATION  No.  106 


PRESS  OF  J.  B.  LIPPINCOTT  COMPANY 
PHILADELPHIA 


THE  GASES  IN  ROCKS. 


It  has  been  known  for  a  long  time  from  microscopical  studies  that 
some  minerals  inclose  minute  cavities  which  contain  both  liquid  and  gas- 
eous matter.  For  a  much  shorter  period  it  has  been  known  that  various 
igneous  rocks,  when  exposed  to  red  heat  in  a  vacuum,  evolve  several  times 
their  volume  of  gas  of  quite  variable  composition.  Since  these  gases  occur 
in  proportions  entirely  different  from  those  of  the  constituents  of  the  air, 
it  has  not  seemed  probable  that  they  were  derived  directly  from  our 
present  atmosphere,  unless  the  rocks  manifest  some  power  of  selective 
absorption  not  now  understood.  The  apparent  difficulties  involved  in  this 
conception  have  suggested  that  some  earlier  atmosphere  was  rich  in  those 
gases.  This  involves  a  hypothesis  relative  to  the  changes  through  which 
the  atmosphere  has  passed,  and  leads  on  to  a  theory  of  its  origin  and  that 
of  the  earth  itself.  An  alternative  hypothesis  regards  these  gases,  not  as 
the  products  absorbed  by  a  molten  earth  from  its  surrounding  gaseous 
envelope,  but  as  entrapped  in  the  body  of  the  earth  during  its  supposed 
accretion,  and  hence  that  they  are  a  source  from  which  accessions  to  our 
present  atmosphere  might  be  derived. 

A  study  of  these  gases  in  the  rocks  has  seemed,  therefore,  to  give 
promise  of  results  of  some  value  to  atmospheric  problems  and,  perhaps,  to 
those  of  cosmogony.  Because  of  this,  it  appeared  advisable  to  determine 
more  widely  the  range  and  the  distribution  of  these  gases,  their  relations 
to  other  geologic  phenomena,  and  the  states  in  which  the  gases,  or  gas- 
producing  substances,  exist  in  the  rocks.  The  desirability  of  supplementary 
work  will  become  more  evident  when  it  is  noted  that,  while  a  considerable 
number  of  investigators  have  analyzed  the  gases  in  rocks,  as  will  appear  in 
the  following  historical  statement,  nearly  all  have  contented  themselves 
with  a  few  determinations,  and  that  even  a  full  compilation  of  all  such 
results  leaves  much  to  be  desired  from  a  geological  point  of  view. 

HISTORICAL  SKETCH. 

As  early  as  1818  the  attention  of  Sir  David  Brewster  was  called  to  the 
subject  of  inclosed  water  by  the  explosion  of  a  crystal  of  topaz  when 
heated  to  redness  ;  but  his  studies  were  not  published  until  1826.  In  the 
mean  time,  Sir  Humphry  Davy  opened  the  cavities  in  a  few  crystals  and 
examined  chemically  the  imprisoned  liquid  and  gas.1  Piercing  a  cavity  in 
several  cases  suddenly  caused  the  inclosed  gas-bubble  to  contract  to  from 
one-sixth  to  one-tenth  of  its  original  volume.  The  gas  was  thought  to  be 
pure  nitrogen.  The  basaltic  rock  from  the  neighborhood  of  Vicence  con- 

lSir  Humphry  Davy,  Phil.  Trans.  1822,  Pt.  n,  pp.  367-376  :  Ann.  de  Chim.  et  Phys., 
t.  21  (1822),  pp.  132-143. 

3 


4  THE    GASES   IN    ROCKS. 

tained  gas  (supposedly  nitrogen)  in  a  still  more  rarefied  state,  as  its  density 
was  60  to  70  times  less  than  that  of  the  atmospheric  air.  Upon  perforating 
a  cavity  in  a  quartz  crystal  from  Dauphine",  an  almost  perfect  vacuum  was 
discovered.  Davy  regarded  the  rarefied  condition  of  the  inclusions  in  the 
crystals  as  strong  evidence  that  the  waters  and  gases  did  not  penetrate 
the  crystals  at  ordinary  temperatures  and  pressures.  This  he  believed  a 
decisive  argument  in  favor  of  the  Huttonian,  or  Plutonian,  school.  How- 
ever, a  crystal  from  Brazil  gave  a  very  different  result;  an  immediate 
expansion  to  a  volume  10  to  12  times  greater  than  the  original  followed  the 
opening  of  a  cavity.  The  composition  of  the  gas  was  not  determined.  The 
existence  of  compressed  gas  in  the  same  sort  of  cavities  seems  adverse  to  the 
conclusions  which  Davy  based  upon  his  earlier  experiments,  but  he  sought 
to  explain  the  difference  by  supposing  the  crust  to  have  been  formed  under 
a  pressure  more  than  sufficient  to  balance  the  expansion  due  to  the  heat. 

Brewster1  attacked  the  problem  by  observing  the  temperature  at  which 
the  inclosed  liquid  passed  over  into  the  gaseous  state.  A  number  of  tests 
showed  this  to  range  from  74°  to  84°  F.  When  raised  to  this  temperature 
the  vacuity  always  reappeared.  Brewster  interpreted  as  follows : 

The  existence  of  a  fluid  which  entirely  fills  the  cavities  of  crystals  at  a  temperature 
varying  from  74°  to  84°  may  be  held  as  a  proof  that  these  crystals  were  formed  at  the 
ordinary  temperature  of  the  atmosphere. 

For  thirty  years  after  Brewster  the  field  was  neglected  until,  in  1858, 
Simmler2  reviewed  Brewster's  work  in  the  light  of  advancing  scientific 
knowledge.  Studying  the  liquid  inclusions  in  quartz,  topaz,  amethyst, 
garnet,  and  other  minerals,  he  arrived  at  the  conclusion  that  the  power  of 
expansion  of  the  liquid  in  these  inclusions  showed  it  to  be  carbon  dioxide. 
Some  years  later  Sorby,  continuing  the  researches  along  the  lines  suggested 
by  Brewster  and  Simmler,  found  that  the  amount  of  expansion  of  liquid 
carbon  dioxide  from  0°  C.  to  30°  C.  corresponded  closely  to  that  observed 
in  the  liquid  of  the  sapphires  with  which  he  experimented.3  In  these  sap- 
phires it  was  noted  that  the  liquid  disappeared  when  warmed  to  approxi- 
mately 30°  C.  As  the  critical  temperature  for  carbon  dioxide,  above  which 
no  amount  of  pressure  will  condense  it  to  a  liquid,  is  30.92°  C.  (87.7°  F.), 
there  remained  little  room  for  doubt  that  the  gas  was  largely  carbon 
dioxide.  Sorby  remarked  that  this  gas  "  might  have  been  inclosed,  either 
as  a  highly  dilated  liquid  or  as  a  highly  compressed  gas;  but  since  the 
other4  liquid  has  deposited  crystals  which  dissolve  on  the  application  of 
heat,  it  seems  most  probable  that  the  water  was  caught  up  in  a  liquid 
state,  sometimes,  perhaps,  holding  a  considerable  amount  of  carbon  dioxide 
in  solution  as  a  gas." 

In  the  same  year  Vogelsang  and  Geissler6  heated  quartz  crystals  and, 
passing  an  electric  spark  through  the  gas  thus  liberated,  examined  its 

1  Sir  David  Brewster,  Trans.  Roy.  Soc.  Edinburgh,  vol.  10  (1826),  pp.  1-41 ;  Edin.  Jour, 
of  Science,  vol.  6.  pp.  153-156. 

2R.  T.  Simmler,  Pogg.  Ann.,  vol.  105  (1858),  pp.  460-466. 

SH.  C.  Sorby  and  P.  J.  Butler,  Proc.  Roy.  Soc.,  vol.  17  (1869),  pp.  291-303.  Earlier 
papers  by  Sorby  appeared  as  follows  :  Phil.  Mag.,  4th  series,  vol.  15,  p.  152  ;  Quart.  Jour. 
Geol.  Soc.,  vol.  14  (1858),  p.  453 ;  Proc.  Roy.  Soc.,  vol.  13  (1864),  p.  333. 

*  Saline  water. 

5  Vogelsang  and  Geissler,  Pogg.  Ann.,  vol.  137  (1869),  pp.  56-75. 


HISTORICAL   SKETCH.  5 

spectrum,  which  was  found  to  show  the  presence  of  much  carbon  dioxide, 
together  with  water  and  a  very  weak  trace  of  hydrogen.  The  presence 
of  the  hydrogen  line,  however,  the  authors  were  inclined  to  attribute  to 
water-vapor. 

Further  researches  upon  the  critical  point  of  the  gas  in  mineral  cavities, 
carried  on  by  Hartley,1  yielded  results  varying  from  26°  to  34°  C.  The 
lowering  of  the  temperature  he  ascribed  to  the  presence  of  some  incon- 
densable gas,  perhaps  nitrogen,  while  he  believed  that  the  raising  of  the 
critical  point  observed  in  some  of  the  quartz  specimens  was  due  to  hydro- 
chloric acid. 

Forster2  and  Hawes3  investigated  smoky  quartz,  the  former  distilling 
from  the  Tiefengletscher  crystals  a  brown  fluid  of  an  empyreumatic  odor, 
giving  reactions  for  ammonia  and  carbonic  acid,  from  which  he  concluded 
that  the  coloring  matter  of  smoky  quartz  was  due  to  a  nitrogenous  hydro- 
carbon, decomposable  by  heat;  the  latter  made  a  microscopic  study  of  the 
liquid  carbon  dioxide  in  the  bubbles  of  the  cavities. 

Investigations  which  have  opened  up  a  broader  field  were  begun  by 
Graham4  in  1867  upon  the  Lenarto  meteoric  iron.  By  submitting  a  strip 
of  the  iron  to  a  red  heat  in  a  vacuum  for  35  minutes  he  obtained  5.38  cubic 
centimeters  of  gas  from  5.78  cubic  centimeters  of  the  metal.  Heated  for  an 
additional  100  minutes,  there  were  evolved  9.52  cubic  centimeters  of  gas 
having  the  folio  wing  composition:  H2, 85.68;  CO,  4.46;  CO2,none;  N2,9.86. 

As  this  meteorite  yielded  about  three  times  its  volume  of  gas,  and 
since  "it  has  been  found  difficult,  on  trial,  to  impregnate  malleable  iron 
with  more  than  an  equal  volume  of  hydrogen,  under  the  pressure  of  our 
atmosphere,"  Graham  drew  the  inference  that  this  meteorite  came  from  a 
body  having  a  dense  atmosphere  of  hydrogen  gas.  By  the  same  process 
Mallet8  extracted  3.17  volumes  of  gas  from  a  Virginia  meteorite.  His 
results  were  in  accordance  with  those  of  Graham:  H2,  35.83;  CO,  38.33; 
C02,  9.75;  N2,  16.09. 

Wohler6  heated  to  redness  some  of  the  metallic  granules  from  the  iron 
basalt  of  Ovifak,  Greenland,  obtaining  more  than  100  volumes  of  gas  which 
burned  with  a  bluish  flame  (mostly  carbon  monoxide  mixed  with  a  little 
of  the  dioxide).  His  results,  however,  were  vitiated  by  having  used  an 
iron  combustion  tube. 

Pursuing  the  method  adopted  by  Graham  and  Mallet,  A.  W.  Wright7 
conducted  a  series  of  experiments  on  meteorites,  which  have  remained  to 
the  present  day  the  source  of  most  of  our  knowledge  of  the  gas  content  of 
these  interesting  bodies.  Wright's  chief  contribution  lies  in  his  two  tables 
showing  that  there  is  a  marked  difference  between  the  gas  contents  of  the 
iron  and  stony  types  of  meteorites;  for  while,  in  the  former,  hydrogen  is 

*W.  N.  Hartley,  Jour.  Chem.  Soc.  (1876),  vol.  2,  pp.  237-250. 
2  A.  Forster,  Pogg.  Ann.,  143  (1871),  pp.  173-194. 
3G.  W.  Hawes,  Am.  Jour.  Science,  vol.  21  (1881),  pp.  203-209. 
4Thos.  Graham,  Proc.  Roy.  Soc.,  vol.  15  (1867),  p.  502. 

6  J.  W.  Mallet,  Proc.  Roy.  Soc.,  vol.  20  (1872),  pp.  365-370. 
8F.  Wohler,  Pogg.  Ann.,  146  (1872),  pp.  297-302. 

7  A.  W.  Wright,  Am.  Jour.  Science,  vol.  9  (1875),  pp.  294-302  and  459-460;   vol.  11 
(1876),  pp.  253-262;  vol.  12  (1876),  pp.  165-176. 


THE    GASES   IN   ROCKS. 


the  most  abundant  gas,  carbon  dioxide  is  the  most  characteristic  con- 
stituent of  the  latter.     His  analyses  are  given  in  table  1. 

TABLE  1. 


Meteorite. 

C02. 

CO. 

CH4. 

H«. 

N2. 

Vol. 

Iron  meteorites  : 
Tazewell  County,  Tenn  
Shingle  Springs,  Cal  
Arva,  Hungary  

14.40 
13.64 
12.56 

41.23 

12.47 
67.71 

42.66 
68.81 
18.19 

1.71 
5.08 
1.54 

3.17 
0.97 
47.13 

Texas 

859 

1462 

7679 

129 

Dickson  County,  Tenn  
Stony  meteorites  : 
Guernsey,  Ohio  
Pultusk  Poland  

13.30 

59.88 
60.29 

15.30 

4.40 
4.35 

2.05 
3.61 

71.40 

31.89 
29.50 

1.78 
2.25 

2.2 

2.99 
1.75 

Parnallee  India  

81.02 

1.74 

2.08 

13.59 

1.57 

2.63 

Weston  Conn   

80.78 

2.20 

1.63 

13.06 

2.33 

3.49 

Iowa  County,  la  

3544 

1.80 

0.0 

57.88 

4.88 

2.50 

This  table  shows  that  in  the  iron  meteorites  carbon  dioxide  in  no  case 
constituted  more  than  15  per  cent  of  the  gas  evolved,  while  in  every  case 
but  one  the  quantity  of  carbon  monoxide  was  considerably  greater.  In 
the  stony  meteorites  carbon  monoxide  is  low,  while  carbon  dioxide  is,  in 
the  majority  of  analyses,  much  the  most  abundant  gas.  Hydrogen  is  more 
important  in  the  iron  meteorites  than  in  the  stony. 

The  same  experimenter  determined  also  the  gases  given  off  by  the  same 
meteorite  at  different  temperatures.  His  figures  for  the  Iowa  County 
meteorite  are  shown  in  table  2. 

TABLE  2. 


Gas. 

At  100°. 

At  250°. 

Below 
red  heat. 

At  low 
red  heat. 

At  full 
red  heat. 

Carbon  dioxide 

9546 

9232 

4227 

3582 

556 

Carbon  monoxide 

00 

182 

511 

049 

000 

Hydrogen 

454 

586 

4806 

5851 

8753 

Nitrogen 

000 

000 

456 

5  18 

691 

Total  

100.00 

100.00 

100.00 

100.00 

100.00 

The  progressive  decrease  in  the  percentage  of  carbon  dioxide  and  the 
corresponding  increase  of  hydrogen  with  the  elevation  of  the  temperature 
are  striking.  His  inquiries  into  other  phases  of  the  problem  will  be  deferred 
until  the  discussion  of  principles,  where  it  will  be  possible  to  treat  each 
factor  to  better  advantage,  in  its  proper  relation  to  the  whole  subject. 

Several  years  later  Wright  applied  his  method  of  gas  extraction  and 
reliable  quantitative  analysis  to  the  gases  in  smoky  quartz,1  which  here- 
tofore had  been  subjected  chiefly  to  qualitative  microscopical  studies- 
However,  only  one  determination  was  made — that  of  a  crystal  from 
Branchville,  Connecticut,  which  yielded  a  small  quantity  of  gas  of  the 
following  composition:  Carbon  dioxide,  98.33;  nitrogen,  1.67;  hydrogen 
sulphide,  sulphur  dioxide,  ammonia,  fluorine,  and  chlorine,  trace. 

1  Wright,  Am.  Jour.  Science,  vol.  21  (1881),  pp.  209-216. 


HISTORICAL    SKETCH. 


Wright  regarded  the  fluorine  and  chlorine  as  being  combined,  and  the 
ammonia  as  probably  existing  together  with  some  of  the  carbon  dioxide  in 
the  form  of  ammonium  carbonate.  The  amount  of  water  obtained,  calcu- 
lated as  vapor,  was  slightly  more  than  twice  the  volume  of  carbon  dioxide. 

Following  Wright,  Sir  James  Dewar,1  in  collaboration  with  Mr.  Ansdell, 
made  several  more  analyses  of  the  meteoritic  gases,  and  then,  in  an 
endeavor  to  discover  the  source  and  significance  of  these  gases,  directed  a 
series  of  experiments  upon  the  theory  that  graphite  might  be  the  retentive 
or  generative  constituent.  Their  analyses  of  the  gases  from  graphites  and 
from  the  matrix  from  which  graphites  have  come  revealed  moderately 
high  volumes.  TABLE  3 


Material. 

Sp.gr. 

Vol. 

CO,. 

CO. 

H2. 

CH4. 

Mb, 

Celestial  graphite 

226 

725 

9181 

250 

540 

01 

Borrodale  graphite 

286 

260 

3640 

777 

222 

2611 

666 

205 

255 

5741 

616 

1025 

2083 

416 

Ceylon  graphite  
Unknown  graphite  

2.25 
1.64 

0.22 
7.26 

66.60 
50.79 

14.80 
3.16 

7.40 
2.50 

3.70 
39.53 

4.50 
3.49 

245 

532 

8238 

238 

1361 

047 

120 

Feldspar 

259 

127 

9472 

081 

221 

061 

140 

Because  the  quantity  of  gas  yielded  by  these  specimens  of  graphite  was 
so  considerable,  Dewar  proceeded  to  ascertain  whether  graphite  could 
absorb  the  different  gases  when  allowed  to  stand  in  each  of  them  for  12 
hours.  His  experiments  with  the  celestial  graphite  which  had  previously 
been  deprived  of  its  gases  indicated  that  little  or  no  absorption  had  taken 
place.  "  It  is  therefore  evident,"  says  Dewar,  "  that  the  large  quantities 
of  gas  occluded  in  celestial  meteorites  can  not  be  explained  by  any  special 
absorptive  power  of  this  variety  of  carbon."  Attempts  to  split  up  the 
hydrogen-producing  compound  with  strong  nitric  acid  and  also  to  wash 
out,  with  ether,  the  possible  carbonaceous  source  of  the  methane,  appeared 
to  show  that  the  hydrogen  existed  in  a  very  stable  compound,  and  that, 
while  the  ether  lessened  the  quantity  of  methane  which  the  graphite  after- 
wards furnished,  it  did  not  dissolve  out  all  the  carbonaceous  compounds 
present,  or  else  that  the  marsh-gas  was  subsequently  formed  during  the 
heating  of  the  material. 

Dewar's  analyses  of  gases  from  stony  meteorites,  which  are  in  accord 
with  Wright's  results,  are  given  in  table  4. 

TABLB  4. 


Meteorite. 

Sp.  gr. 

Vol. 

C02. 

CO. 

Hs. 

CH4. 

N2. 

Dhurmsala,  India  
Pultusk 

3.175 
3718 

2.51 
354 

63.15 
6612 

1.31 
540 

28.48 
1814 

3.9 
765 

1.31 
2.69 

Mocs 

367 

194 

6450 

390 

2294 

441 

3.67 

Pumice  stone         .    .  . 

250 

055 

3950 

1850 

254 

16.60 

An  analysis  of  the  gas  extracted  from  the  Orgueil  meteorite  revealed 
much  sulphur  dioxide,  which  Professor  Dewar  believed  to  have  been  derived 

1  Dewar  and  Ansdell,  Proc.  Roy.  Inst.,  vol.  11  (1884-1886),  p.  332  and  pp.  541-552. 


8  THE    GASES   IN   BOCKS. 

from  the  decomposition  of  sulphate  of  iron.  In  all,  57.87  volumes  were 
obtained:  CO2,  12.77;  CO,  1.96;  CH4,  1.50;  N2,  0.56;  SO2,  83.  Leaving 
out  the  SO2,  9.8  volumes  remain,  as  follows:  CO2,  76.05;  CO,  11.67;  CH4, 
8.93;  N2,  3.33.  This  analysis,  the  most  remarkable  of  the  series,  though 
Dewar  does  not  mention  the  fact,  shows  a  complete  absence  of  hydrogen 
(an  uncommon  phenomenon),  while  the  percentage  of  marsh-gas  is  unusu- 
ally high.  There  is,  however,  reason  to  suspect  that  there  was  hydrogen 
liberated,  but  that  it  was  oxidized  to  water  by  the  action  of  the  iron  com- 
pound, following  the  decomposition  of  the  sulphate. 

In  1888  W.  F.  Hillebrand1  discovered  that  the  mineral  uraninite  when 
treated  with  acids  slowly  disengaged  bubbles  of  gas.  As  the  result  of  a 
well-selected  series  of  tests  this  appeared,  in  the  light  of  the  chemical 
knowledge  of  that  day,  to  be  nitrogen.  Trials  with  different  varieties  of 
the  mineral  revealed  a  rather  significant  relation  between  the  percentage  of 
uranyl  and  this  gas.  The  greater  the  amount  of  the  oxide,  the  more  gas 
obtained. 

Several  years  later,  Sir  William  Ramsay's  scepticism  was  aroused  when 
his  attention  was  called  to  the  paper  by  Hillebrand,  for  he  hesitated  to  be- 
lieve that  free  nitrogen  could  be  produced  by  treating  any  substance  with 
sulphuric  acid.  To  test  the  case,  he  decomposed  cleveite  with  this  acid, 
obtaining  little  nitrogen,  but  some  20  cubic  centimeters  of  argon,  which 
the  spectroscope  showed  to  be  mixed  with  some  other  gas.2  A  brilliant 
yellow  line  which  appeared  in  this  spectrum  coincided  exactly  with  D3,  the 
so-called  "  helium  "  line,  first  discovered  in  the  spectrum  of  the  chromo- 
sphere of  the  sun  by  Sir  Norman  Lockyer  in  1868.  This  was  the  first  real 
acquaintance  with  helium,  until  then  known  only  as  a  hypothetical  sub- 
stance existing  in  the  sun.  Lockyer  immediately  became  interested  in  this 
discovery  of  helium  in  a  terrestrial  mineral,  and  attempted  to  prove  that 
it  was  not  a  single  gas,  but  a  compound  or  a  mixture  of  gases,  basing  his 
contention  upon  various  strange  lines  in  the  spectrum.3 

Ramsay,  continuing  his  study  of  the  gas  from  cleveite,  perceived  what 
had  been  previously  overlooked,  namely,  that  hydrogen  generally  was  more 
abundant  than  helium — in  one  case  amounting  to  80  per  cent  of  the  total 
gas.  The  hypothesis  that  this  hydrogen  might  have  been  formed  by  the 
breaking  up  of  an  unstable  hydride,  the  form  in  which  Ramsay  thought 
the  helium  should  be  evolved,  if  it  were  derived  from  combination  with  the 
uranium  or  yttrium  of  the  mineral,  was  put  to  the  test,  with  the  result 
that  the  evidence  pointed  strongly  against  the  theory.4  A  series  of  miner- 
als powdered  and  fused  with  potassium  acid  sulphate  were  found  to  yield 
gas,  sometimes  helium,6  but  oftener  hydrogen  and  the  oxides  of  carbon.6 

In  1896  W.  A.  Tilden  made  an  attempt  to  determine  the  condition  in 
which  helium  and  the  associated  gases  exist  in  minerals.  Argon  and  helium 
were  of  particular  interest,  for  Tilden  believed  that  these  two  elements  will 

1W.  F.  Hillebrand,  Bull.  78,  U.  S.  G.  S.,  pp.  43-79. 

2  Sir  William  Ramsay,  Proc.  Roy.  Soc.,  vol.  68  (1895),  pp.  65-67. 

3  Sir  J.  N.  Lockyer,  a  series  of  six  short  papers  in  Proc.  Roy.  Soc.,  vols.  58,  59,  and  60. 

4  Ramsay,  Proc.  Roy.  Soc.,  vol.  58,  pp.  81-89. 

5  Ramsay,  Proc.  Roy.  Soc.,  vol.  59,  pp.  325-330. 

1  Ramsay  and  Travers,  Proc.  Roy.  Soc.,  vol.  60,  pp.  442-448. 


HISTOKICAL   SKETCH. 


not  be  found  to  enter  into  combination  at  such  temperatures  as  are  ordi- 
narily attainable.     In  his  own  words: 

It  also  appears  improbable  that  in  the  minerals  from  which  the  mixture  of  gases  con- 
taining helium  has  been  extracted  this  element  exists  in  a  state  of  ordinary  chemical  com- 
bination, for,  on  treating  the  mineral  with  acids,  no  compound  of  helium  with  hydrogen  has 
yet  been  observed,  and  the  components  of  the  minerals  are  of  a  kind  which  are  commonly 
regarded  as  chemically  saturated.1 

The  minerals  monazite  and  cleveite  were  found  to  yield  gas  at  low  tem- 
peratures (60°  and  110°,  respectively),  carbon  dioxide  appearing  first.  The 
monazite  heated  to  130°  to  140°  gave  gas  which,  for  the  first  time,  showed 
the  DZ  line,  indicating  the  presence  of  helium.  Between  140°  and  250° 
there  was  obtained  carbon  dioxide  with  about  one-fourth  of  its  volume  of 
a  gas  rich  in  helium.  At  higher  temperatures  up  to  446°  (boiling  sulphur) 
there  was  less  gas  evolved.  Cleveite  behaved  in  a  similar  way.  Studies 
on  the  absorption  of  helium  by  cleveite  demonstrated  that  the  mineral 
does  not  absorb  this  gas  at  the  ordinary  pressure,  although  placed  in  a 
helium  atmosphere  for  nine  weeks.  But  under  pressure  of  2.5  and  7  atmos- 
pheres, Tilden  believed  that  he  obtained  an  appreciable  absorption.  A 
trial  with  the  Peterhead  granite,  which  contained  no  helium  in  the  first 
place,  proved  that  the  granite  would  absorb  none  of  the  gas  whatever, 
even  aided  by  a  pressure  of  7  atmospheres. 

The  finding  of  hydrogen  as  well  as  carbon  dioxide  in  this  Peterhead 
granite2  led  Tilden  to  investigate  the  gases  inclosed  in  crystalline  rocks.3 
His  five  complete  analyses  are  as  given  in  table  5. 

TABLE  5. 


Rock. 

C02. 

CO. 

CH4. 

H2. 

N,. 

Granite  Skye 

2360 

645 

302 

6168 

513 

550 

216 

203 

8842 

190 

Pyroxene  gneiss,  Ceylon  
Gneiss,  Seringapatam  

77.72 
31.62 

8.06 
5.36 

0.56 
0.51 

12.49 
61.93 

1.16 
0.56 

Basalt,  Antrim  

32.08 

20.08 

10.00 

36.15 

1.61 

In  addition  to  these  analyses,  25  carbon-dioxide  determinations  were 
made. 

Tilden  believed  the  gas  to  be  "  wholly  inclosed  in  cavities  which  are 
visible  in  thin  sections  of  the  rock  when  viewed  under  the  microscope. 
*  *  *  To  account  for  the  large  proportion  of  hydrogen  and  carbon 
dioxide  in  these  gases,  it  is  only  necessary  to  suppose  that  the  rock  inclos- 
ing them  was  crystallized  in  an  atmosphere  rich  in  carbon  dioxide  and 
steam,  which  had  been,  or  were  at  the  same  time,  in  contact  with  some 
easily  oxidizable  substance,  at  a  moderately  high  temperature.  Of  the 
substances  capable  of  so  acting,  carbon,  a  metal,  or  a  protoxide  of  a  metal 
present  themselves  as  the  most  probable."  Hydrogen  and  carbon  monox- 

1 W.  A.  Tilden,  Proc.  Roy.  Soc.,  vol.  59  (1896),  p.  218. 

2  Wright's  two  analyses,  showing  that  trap  rocks  yield  much  the  same  gases  as  meteor- 
ites, also  served  to  call  attention  to  this  field  for  investigation. 

3  Tilden,  Chem.  News,  vol.  75  (1897),  pp.  169-170. 


10 


THE    GASES   IN    ROCKS. 


ide  might  then  be  produced  by  the  reducing  action  of  metallic  iron  or  fer- 
rous oxide  upon  steam  and  carbon  dioxide  at  high  temperature,  according 
to  the  reactions — 


3Fe  +  4H2O  =  Fe304  +  4H2 


3Fe  +  4C02  =  Fe3O4  +  4CO 


The  origin  of  the  marsh-gas  is  assigned  in  this  paper  to  the  action  of 
water  at  high  temperature  upon  metallic  carbides,  or  similar  compounds, 
in  the  earth's  interior,  as  suggested  by  Mendele*ef 1  and  the  more  recent 
studies  of  Moissan.2 

A  year  after  the  publication  of  Tilden's  article,  criticism  of  his  paper, 
and  in  fact  of  the  work  of  all  previous  investigators  in  this  line,  was  made 
by  M.  W.  Travers,  who  undertook  to  prove  that  the  different  gases,  not 
excluding  even  argon  and  helium,  did  not  exist  in  the  gaseous  state  in  min- 
erals, but  were  formed  by  chemical  interaction  between  the  non-gaseous 
materials  in  the  combustion-tube.3  The  key  to  his  position  lay  in  the  two 
reversible  reactions — 


3FeO  +  H2O  =  Fe3O4  +  H2 


3FeO  +  CO2  =  Fe3O4  +  CO 


His  table  revealed  a  certain  relation  between  the  hydrogen  and  carbon 
monoxide  produced,  and  the  quantity  of  ferrous  oxide  and  water  present 
in  the  mineral.  It  is  shown  in  table  6.  The  figures  for  FeO  and  H2O  refer 
to  the  percentages  in  the  rock;  the  gases  are  expressed  in  cubic  centimeters 
per  gram  of  rock. 

TABLE  6. 


Mineral. 

FeO. 

H,0. 

H» 

CO. 

C04. 

Chlorite  Moravia  

106 

46 

2180 

0494 

0123 

Serpentine,  Zermatt  .       

27 

95 

0800 

None 

None. 

Gabbro,  Isle  of  Skye  

61 

15 

0490 

None 

None. 

Mica,  Westehester,  Pa  
Foliated  talc  Tyrol  

1.4 
04 

0.13 
45 

0.08 
004 

0.150 
0070 

Feldspar  Peterhead        

21 

100 

0214 

1201 

Four  of  these  (including  the  mica  of  meta-sedimentary  origin)  were 
secondary  minerals  whose  gas  may  have  been  produced  entirely  by  chem- 
ical reactions  in  the  tube,  without  having  very  great  bearing  upon  the 
problem  of  the  gas-content  of  primary  minerals  and  rocks  which  have  not 
undergone  extensive  weathering  and  alteration.  The  only  rock  tried,  the 
gabbro,  may  be  pointed  out  as  unique  in  yielding  only  hydrogen  without 
either  of  the  oxides  of  carbon  or  nitrogen. 

Armand  Gautier,4  in  1901,  came  to  the  conclusion  that  the  gases  which 
he  obtained  from  several  igneous  rocks  did  not  escape  from  inclusions,  for 
the  most  part,  but  were  products  of  chemical  reactions  at  raised  tempera- 
tures. A  small  quantity  of  gas  was  obtained  by  heating  granite  powder, 
moistened  with  pure  water,  up  to  300°  in  a  vacuum.  By  heating  the  same 

1  Mendele"ef,  Prin.  of  Chem.,  transl.  of  Kamensky  and  Greenaway,  vol.  1,  pp.  364-365. 
2H.  Moissan,  Proc.  Roy.  Soc.,  vol.  60  (1896),  pp.  156-160. 
3M.  W.  Travers,  Proc.  Roy.  Soc.,  vol.  64  (1898),  pp.  130-142. 
4  A.  Gautier,  Comptes  Rendus,  vol.  132,  pp.  58-64,  189-194. 


HISTORICAL    SKETCH. 


11 


granite  powder  together  with  a  mixture  of  two  parts  of  sirupy  phosphoric 

acid  and  one  part  of  water  to  only  100°,  he  received  more  than  10  times  as 

much  gas  as  was  evolved  at  300°  without  the  acid,  or  about  1.5  volumes. 

Table  7  comprises  Gautier's  analyses  of  the  gases  expelled  at  red  heat. 


TABLE  7. 


Rock. 

H»8. 

C02. 

CO. 

CH4. 

H*. 

N,. 

Vol. 

Granite  Vire  I  

Trace 

14.80 

493 

224 

7730 

083 

IAv 

Granite,  Vire  II.  ..         .              .... 

171 

898 

512 

109 

8280 

042 

69 

Granite  Vire  III.  .... 

069 

1442 

550 

199 

7680 

040 

Granitoid  porphyry  Esterel 

000 

5925 

420 

253 

3109 

210 

76 

Ophite  Villefranqae  I 

344 

2810 

391 

140 

6328 

005 

)Av 

Ophite  Villefranque  II 

556 

3066 

445 

066 

5890 

013 

760 

Ophite  Villefranque  III 

045 

35  71 

4  85 

1  99 

5629 

068 

Lherzolite,  Lherz  

11.85 

78.35 

1.99 

0.01 

7.34 

Trace 

15.7 

The  r61e  played  by  these  gases  in  vulcanism,  and  their  connection  with 
thermal  waters,  is  discussed  in  more  recent  papers.1  Following  Gautier, 
Huttner2  showed  by  a  series  of  experiments  that  when  a  stream  of  dry  car- 
bon dioxide  is  passed  over  a  rock  powder  at  a  temperature  of  800°,  carbon 
monoxide  results,  owing  to  a  reduction  of  the  dioxide,  as  this  investigator 
believes,  by  some  of  the  hydrogen  given  off  from  the  rock.  As  the  miner- 
als orthite  and  gadolinite  yielded  no  carbon  monoxide,  though  abundant 
hydrogen,  when  gelatinized  in  hydrochloric  acid,  he  came  to  the  conclusion 
that  this  gas  does  not  exist  in  rocks. 

In  1905  there  appeared  a  paper  by  Albert  Brun,3  "Quelques  Recherches 
sur  le  Volcanisme,"  based  upon  studies  of  lavas  from  Vesuvius,  Stromboli, 
and  other  Mediterranean  volcanoes.  While  no  complete  gas  analyses  were 
undertaken,  much  experimentation  was  done,  covering  the  expulsion  of 
gases  and  vapors  at  or  near  the  fusion  point  of  the  lavas.  This  author  ex- 
presses the  opinion  that  it  is  the  liquefaction  of  the  rock  which  produces 
the  gases,  these  being  engendered  by  chemical  bodies  contained  within  the 
lava  itself.  The  gases  recognized  are  nitrogen  and  its  derivative  ammonia, 
chlorine  with  derived  hydrochloric  acid,  and  hydrocarbons.  The  nitrogen 
is  assigned  to  nitrides,  and  the  ammonia  to  reactions  between  nitrides  and 
hydrocarbons,  while  a  dissociation  of  chlorides  furnishes  free  chlorine  which 
may  take  hydrogen  from  hydrocarbons  to  form  hydrochloric  acid.  A 
source  for  hydrogen  and  carbon  dioxide  is  recognized  in  hydrocarbon  com- 
pounds, though  Brun  was  less  interested  in  the  gases  expelled  below  the 
melting-point  of  the  lava. 

1  Gautier,  Comptes  Rendus,  vol.  132,  pp.  740-746  and  932-938 ;  Economic  Geology, 
vol.  1  (1906),  pp.  688-697. 

2K.  Huttner,  Zeitschrift  fur  Anorg.  Chem.,  43  (1905),  pp.  8-13. 
3  A.  Brun,  Archives  des  Sciences  phys.  et  naturelles,  Geneve,  1905. 


12  THE    GASES   IN   ROCKS. 

METHOD  OF  PROCEDURE. 

To  obtain  the  gases  for  these  investigations,  the  general  methods  of 
Graham,  Mallet,  and  Wright  were  adopted,  though  the  details  of  the  appa- 
ratus were  modified  in  many  particulars.  The  gas  is  extracted  from  the 
rock  material  which  has  been  finely  pulverized,  by  heating  the  powder  in  a 
vacuum.  For  this  purpose  an  apparatus  consisting  of  a  combustion-tube 
connected  with  a  mercury-pump  capable  of  producing  and  maintaining  a 
vacuum  of  a  fraction  of  a  millimeter  pressure  is  required.  Simplicity  being 
desirable  in  order  to  insure  the  uniform  working  of  the  pump  in  the  pres- 
ence of  corrosive  gases,  such  as  hydrogen  sulphide  and  sulphur  dioxide, 
which  attack  and  befoul  the  mercury,  the  most  elementary  type  of  Topler1 
pump  was  used  in  these  experiments. 

To  the  receiving  end  of  the  pump  a  long,  horizontal,  calcium  chloride 
drying-tube  is  fused.  The  ideal  method  would  be  to  seal  the  combustion- 
tube  containing  the  rock  powder  directly  to  the  free  end  of  this  drying- 
tube.  But  inasmuch  as  the  pump  and  drying-tube  are  both  constructed 
of  soft  glass,  whereas  the  tube  in  which  the  high-temperature  combustions 
are  to  be  made  must,  of  necessity,  consist  of  the  most  refractory  glass,  which 
can  not  be  readily  united  to  the  fusible  glass,  one  break  in  the  system  is 
unavoidable.  This  is  made  at  the  end  of  the  drying-tube,  which  is  ground 
so  as  to  receive  a  tightly  fitting  hollow  stopper  of  the  same  hard,  blue 
Jena  composition  tubing  as  the  combustion-tube.  A  5-millimeter  tube  of 
blue  Jena  glass  joins  the  combustion-tube  to  the  stopper,  and  is  taken  of 
sufficient  length  to  allow  of  repeated  cutting  and  resealing  to  successive 
tubes,  as  they  become  useless  from  slow  deformation  under  the  combined 
influence  of  high  temperature  and  vacuum. 

The  capillary  exhaust-tube  of  the  pump,  dipping  under  mercury  in 
a  trough,  is  bent  upward  at  its  lower  extremity,  so  as  to  deliver  the  gas 
expelled  from  the  pump  directly  into  the  receptacle  designed  for  holding 
it.  For  this  purpose,  a  separatory  funnel  of  about  125  cubic  centimeters 
capacity,  held  by  a  clamp  in  an  inverted  position  over  the  mercury  trough, 
proved  most  serviceable. 

In  making  an  analysis,  the  rock  specimen  is  first  reduced  to  a  powder 
of  sufficient  fineness  to  pass  through  a  sieve  of  30  meshes  to  the  inch.  A 
portion  of  this  powder,  roughly  estimated  to  approach  the  maximum 
quantity  which  can  with  safety  be  placed  in  the  combustion-tube,  is  then 
weighed  and  carefully  poured  into  the  tube  through  the  hollow  stopper, 
which,  on  account  of  its  shape,  serves  as  a  funnel.  Because  the  rock-dust 
in  falling  becomes  somewhat  packed,  the  tube  must  afterwards  be  held  in 
a  horizontal  position,  and  gently  shaken  or  tapped,  to  establish  a  free  pas- 
sageway for  the  gases,  extending  the  entire  length  of  the  tube;  otherwise, 
upon  attempting  to  exhaust,  preparatory  to  heating,  the  air  entrapped 
in  the  powder,  having  no  avenue  of  ready  escape,  will  expand  so  rapidly 
as  to  force  some  of  the  material  into  the  drying-tube. 

Thus  carefully  filled,  the  tube  is  placed  in  the  combustion-furnace, 
which  stands  upon  a  table  of  height  such  that  the  stopper  end  of  the  com- 

1  Described  by  Travers,  A  study  of  gases,  pp.  5-10. 


METHOD    OF    PROCEDURE.  13 

bustion-tube  meets  approximately  the  ground  end  of  the  calcium  chloride 
tube  coming  from  the  pump.  The  pump  itself,  installed  upon  a  specially 
constructed  table  resting  on  jacks,  can  be  raised  or  lowered,  or  tilted  at  a 
slight  angle  in  any  direction  necessary  to  enable  the  stopper  protruding 
from  the  furnace  to  fit  exactly  into  the  drying-tube.  As  the  whole  appa- 
ratus is  now  rigid  glass  from  end  to  end,  care  is  required  in  fitting  the  two 
parts  together,  lest  there  be  strain  sufficient  to  cause  serious  fracture. 
To  prevent  leakage  during  the  extraction  of  the  gas,  the  ground-glass 
connection  (the  only  source  of  leakage)  is  completely  incased  in  a  thick 
coating  of  paraffine,1 

The  air  in  the  apparatus  is  now  pumped  off  until  the  exhaustion  can 
be  carried  no  further,  at  which  point  the  pressure  may  be  in  the  neighbor- 
hood of  0.01  millimeter.  If  allowed  to  stand  for  several  days  this  vacuum 
remains  entirely  without  change.  When  ready,  the  burners  in  the  furnace 
are  lighted,  the  separating  funnel  in  which  the  gases  are  to  be  collected  is 
filled  with  mercury,  and  the  evolution  of  the  gas  is  under  way.  As  fast  as 
the  gases  are  liberated  by  the  heat  they  are  pumped  over  into  the  collect- 
ing-funnel— a  process  usually  requiring  about  3  or  4  hours  before  the  last 
traces  of  gas  have  been  expelled. 

ANALYSIS  OF  THE  GAS. 

After  constant  temperature  has  been  established  in  the  room,  the  gas 
is  drawn  from  the  receiver  into  a  Lunge  nitrometer  and  the  carbon  dioxide 
and  hydrogen  sulphide  absorbed  by  the  introduction  of  a  cubic  centimeter 
of  30  per  cent  potassium  hydroxide  solution.  The  remaining  gas  is  trans- 
ferred to  a  gas-burette,  filled  with  water,  after  which  the  remainder  of  the 
analysis  is  carried  on  according  to  the  method  described  by  Hempel.2 
From  the  potassium  hydroxide  solution  the  amount  of  hydrogen  sulphide 
absorbed  is  determined  by  titration  with  N/100  iodine  solution.  If  it  be 
desired  to  measure  the  quantity  of  helium  and  argon,  the  gas  remaining 
after  the  removal  of  all  the  constituents,  except  nitrogen  and  these  inert 
gases,  is  passed  over  metallic  calcium  heated  to  redness.3  This  absorbs  the 
nitrogen,  leaving  only  helium  and  argon,  which  are  examined  spectro- 
scopically. 

1  Whenever  rocks  containing  a  large  proportion  of  quartz  are  tested,  it  is  necessary 
to  substitute  a  porcelain  tube,  since  quartz  scratches  glass,  causing  it  to  crack  when  heated. 
The  connections  are  readily  made  tight  with  paraffine. 

J  Hempel,  Methods  of  gas  analysis  :  Technical  method. 

3  Travers,  A  study  of  gases,  p.  102. 


14 


THE    GASES   IN    ROCKS. 


THE  ANALYSES. 

The  analyses  are  numbered  in  table  8  in  the  order  in  which  they  were 
made,  and  therefore  furnish  a  chronological  account  of  these  investiga- 
tions. At  the  commencement  of  these  studies,  it  being  deemed  advisable 
to  make  a  rapid  survey  of  the  field  and  establish  the  range  of  the  phenome- 
non, in  order  to  direct  later  experiments  more  intelligently,  less  attention 
was  given  to  securing  the  most  trustworthy  method  of  extracting  the  gas. 
Twenty-two  analyses  were  made  during  the  preliminary  trial  stage,  before  the 
apparatus  was  overhauled  and  sealed  glass  connections  substituted  for  rubber 
tubing.  As  it  was  difficult  to  prevent  a  slight  leakage  of  air  into  the  tubes  of 
the  original  apparatus,  the  first  22  analyses  are  characterized  by  a  higher 
percentage  of  nitrogen  than  those  made  afterwards  under  more  favorable 
conditions.  Hydrogen  sulphide  was  not  determined  in  the  first  17  analyses. 

Table  8  gives  the  percentage  of  each  gas  in  the  total  volume  of  gas;  and 
the  volume  of  each  gas  (at  0°  and  760  mm.  pressure)  per  unit-volume  of  rock. 

TABLE  8. 


•3 

S 

B 

"3 

i 

i 

Specimen  No.  and  remarks. 

k 

3 

1 

I 

g 

O 

€ 

| 

I- 

I 

a 

J! 

1 

I 

jz; 

1 

1.  Medium-grained   white   granite,  rather 

P.  ct. 

19.20 

4.94 

4.85 

64.01 

7.00 

100 

low  in  quartz. 

Vol. 

.28 

.07 

.07 

.92 

.10 

1.44 

2.  Very  coarse  granite  with  prominent  pink 
feldspar  phenocrysts. 

P.  ct. 
Vol. 

11.56 
.42 

2.41 
.09 

2.70 
.10 

80.29 
2.94 

3.04 
.11 

100 
3.66 

3.  Keewatin    schist   from   Mesabi  district, 

P.  ct. 

63.76 

2.33 

.43 

31.66 

1.82 

100 

Minn.     From  oldest  known  series  of 

Vol. 

7.67 

.28 

.05 

3.82 

.22 

12.04 

Lake  Superior   region,  highly  carbon- 
ated.    (Specimen   40896,  Slide  15466,  U. 

S.  G.  S.)    From  C.  R.  .Van  Hise. 

4.  Laurentian  dike  rock  from  Lake  Superior. 

P.  ct. 

14.74 

3.93 

2.85 

71.88 

6.60 

100 

(Specimen  41879,  Slide  16673,  U.  S.  G.  S.) 

Vol. 

.31 

.08 

.06 

1.50 

.13 

2.08 

Gneiss  from  contact  of  Keewatin  green- 

stone and  La  urentian  granite  near  Rat 

Portage,  Ont.     From  C.  R.  Van  Hise. 
5.  Kinderhook    shale.     Burlington,   Iowa. 

P.  ct. 

91.65 

3.46 

1.24 

2.18 

1.47 

100 

From  Stuart  Weller. 

Vol. 

9.28 

.35 

.12 

.22 

.15 

10.12 

6.  Portage  shale,  Ithaca,  N.  Y.     From  Dr. 

P.  ct. 

39.80 

22.65 

4.25 

33.30 

100 

Weller.    (Nitrogen  omitted  from  analy- 
sis because  of  leakage  of  air  into  tube.) 

Vol. 

1.47 

.83 

.16 

1.23 

3.69 

7.  Muscovite,  Canada  ;  material  taken  from 

P.  ct. 

70.33 

6.59 

2.74 

5.49 

14.85 

100 

a  large  slab  of  mica  in  Walker  Museum 

Vol. 

1.26 

.12 

.04 

.10 

.27 

1.79 

8.  Potsdam  sandstone,  Baraboo.Wis.    Treat- 

P. ct. 

45.70 

17.19 

." 

s 

36.32 

100 

ed  with  HC1  to  remove  any  carbonate 

Vol. 

.47 

.18 

.C 

1 

.38 

1.04 

9.  Pike's  Peak  granite,  from  carriage-road 

P.  ct. 

60.74 

9.24 

2.70 

6.47 

20.85 

100 

across   divide    between   N.  Cheyenne 

Vol. 

.37 

.05 

.02 

.04 

.12 

.60 

and  Bear  Creek    canyons.     A  coarse- 

grained, yellowish  -pink  granite  consti- 
tuting the  great  mass  into  which  the 

finer-grained    pinkish   granite  of  the 

peak  proper  has  been  intruded. 
10.  Rhyolite,    Marble    Mountain    on   north 

P.  ct. 

44.15 

16.40 

7.14 

5.81 

26.50 

100 

slopes  of  San  Francisco  Peaks,  Ariz. 

Vol. 

.22 

.08 

.04 

.03 

.13 

.50 

11.  Keweenawan  diabase,  from  1  mile  east 

P.  ct. 

12.05 

.93 

3.83 

78.14 

5.05 

100 

of  Dresser  Junction,  Polk  Co.,  Wis.  (a 

Vol. 

.59 

.05 

.19 

3.83 

.25 

4.91 

lava  flow). 

12.  Quartzite  schist,  collected  2  miles  south- 

P. ct. 

46.05 

20.68 

7.93 

7.29 

18.05 

100 

west  of  Baraboo,  Wis. 
13.  Andesite.   Silver  Creek  Basin,  Ouray  Co., 

Vol. 
P.  ct. 

.16 

.07 

36.28 

.03 
7.61 

.03 

27.91 

.06 
28.20 

.35 
100 

Colo. 

Vol. 

.... 

.09 

.02 

.08 

.08 

.27 

14.  Coarse  porphyry  from  dump  pile  of  San 
Pedro  Mine,  Ouray  Co.,  Colo. 

P.  ct. 
Vol. 

.(.V. 

16.15 
.05 

7.51 
.02 

73.00 

3.34 
.01 

100 
.30 

i  Carbonated. 


THE    ANALYSES. 


15 


TABLE  8 — Continued. 


Specimen  No.  and  remarks. 

P.ct. 
or  vol. 

H2S. 

CO,. 

CO. 

CH4. 

Ho. 

ft. 

Total. 

15.  Gabbro  diorite  from  about  13,000  ft.  eleva- 
tion on  south  side  of  Mt.  Sneflels,  Colo. 

P.ct. 
Vol. 

22.01 
.40 

5.54 
.10 

2.05 
.04 

62.33 
1  13 

8.07 
14 

100 
1  81 

16.  Coarse-grained  gabbro  diorite,  summit  of 

P.ct. 

(*) 

10.08 

1.92 

79.15 

8.85 

100 

Mt.  Sneffels,  Colo. 

Vol. 

.12 

.02 

.97 

1.22 

217.  Coarse  orthoclase  gabbro.from  bluff  about 

P.ct. 

12.08 

3.20 

1.79 

o'q7 

100 

100  paces  east  of  the  "  Pavilion,"  in  N.  i 

Vol. 

.44 

.12 

.07 

Ves 

32 

3.63 

sec.  28,  Duluth,  Minn.    Specimen  4602, 

Slide  4602,  U.  S.  G.  S.  This  belongs  to  the 

St.  Louis  River  series  (6000  ft.  thick) 

which  is  the  lowest  member  of  the  Ke- 

weenawan  at  Duluth.    Collection  of  R. 

D.  Irving.     References:  Monograph  v, 

U.  S.  G.  S.,  pp.  50-53,  266,  and  268-275. 

18.  Hamilton  shale,  along  the  Susquehanna, 

P.ct 

0.04 

16.52 

6.91 

2.90 

57.89 

15.75 

100 

1  mile  south  of  Marysville,  Pa.;  a  very 

Vol. 

.00 

.41 

.17 

.07 

L45 

.40 

2.50 

hard  indurated  shale. 

34  19.  Massive  granite  porphyry,  Horse  Race, 
near  Upper  Quinnesec  Falls,  Menominee 

P.ct 
Vol. 

51.26 
3.51 

10.55 
.72 

.86 
.06 

34.19 
2.84 

3.14 

.22 

100 
6.85 

district.    Specimen  11082,  Slide  5700,  U. 
S.  G.  S.    Collection  G.  H.  Williams. 

4  20.  Fine-grained  gneiss,  same  rock-mass  as 

P.ct 

.24 

67.24 

8.31 

.79 

14.96 

8.46 

100 

No.  19.    Specimen  11085,  Slide  5702,  U. 

Vol. 

.00 

1.89 

.23 

.02 

.43 

.23 

2.80 

S.  G.  S.    Collection  G.  H.  Williams. 

4  21.  Fine-grained  banded  gneiss,  same  rock- 

P.ct. 

71.47 

12.20 

.68 

14.75 

.90 

100 

mass  as  Nos.  19  and  20.  Specimen  11084, 

Vol. 

6.63 

1.13 

.06 

1.37 

.08 

9.27 

Slide  5701,  U.  8.  G.  S.   Collection  G.  H. 

Williams. 

22.  Laurentian  granite,  Marquette  district, 

P.ct 

64.41 

4.41 

.93 

25.15 

5.10 

100 

Mich.  Specimen  14392,  Slide  9259.  From 

Vol. 

1.89 

.13 

.03 

.74 

.15 

2.94 

C.  R.  Van  Hise. 

23.  Schist  with  chloritoid,  Black  Hills,  S.  Dak. 

P.ct. 

12.49 

2.56 

1.10 

82.53 

1.32 

100 

Specimen  14928,  Slides  7671,  14968,  and 

Vol. 

.46 

.10 

.04 

3.07 

.05 

3.72 

14969.     References,   Bull.  239,  pi.  xiv. 

Described  by  Van  Hise,  Bull.  G.  S.  A., 
vol.  1.    Developed  by  anamorphism  of 
graywacke-slate  series  through  the  in- 
fluence of  batholithic  granite. 

24.  Pink  orthoclase  granite,  North  Carolina. 
Obtained   from  Blake  &  Co.,  marble 

P.ct 
VoL 

.13 
.00 

23.86 
.16 

8.28 
.05 

3.83 

.02 

57.81 
.38 

6.59 
.04 

100 
.65 

cutters,  Chicago. 

25.  Dark  olive-gray  granite,  Quincy,  Mass. 
From  Blake  &  Co. 

P.ct. 

Vol. 

.10 
.00 

24.56 
.39 

5.48 
.09 

3.40 
.06 

64.84 
1.04 

1.62 
.02 

100 
1.60 

526.  Fine-grained  gray  granite,  Russia.   From 
Blake  &  Co. 

P.ct. 
Vol. 

.03 
.00 

60.43 
1.79 

6.15 
.18 

33.36 
.99 

100 
2.96 

27.  Baltimore  gneiss,  Williams'  quarry,  Rob- 
erts Road,  2  miles  west  of  Bryn  Mawr, 

P.ct. 
Vol. 

.01 

.00 

2.95 
.13 

2.05 
.10 

2.99 
.14 

91.11 
4.32 

.89 
.04 

100 
4.73 

Pa.    From  F.  Bascom. 

28.  Baltimoregneiss,SchuylkillRiversection, 

P.ct 

4.91 

22.17 

3.69 

1.74 

65.85 

1.64 

ICO 

1  mile  SE.  of  Spring  Mill,  Pa.  From  F. 

Vol. 

.30 

1.35 

.22 

.11 

4.02 

.10 

6.10 

Bascom. 

29.  Wissahickon  mica  gneiss,   Fovelton's 

P.ct. 

.53 

19.07 

6.67 

2.21 

67.33 

4.19 

100 

quarry,  on  Childs  estate,  2  miles  SW.  of 
Bryn  Mawr,  Pa.    From  F.  Bascom. 

Vol. 

.00 

.19 

.07 

.02 

.65 

.04 

.97 

30.  Wissahickon  mica  gneiss,  Rose  Glen  quar- 

P.ct 

.06 

8.26 

8.35 

8.50 

81.65 

8.18 

100 

ry  W.  bank  of  Schuylkill  River.  Amore 
solid,  compact  rock  than  No.  29,  which 
was  sericitic.    From  Dr.  Bascom. 

Vol. 

.00 

.19 

.08 

.08 

1.90 

.08 

2.33 

31.  Cambrian  gneiss,   West    Grove   Ridge, 

P.ct. 

33.99 

11.43 

1.21 

49.02 

4.36 

100 

Coatesville  Quadrangle,  Pa.    From  Dr. 

VoL 

.26 

.09 

.01 

.37 

.03 

.76 

F.  Bascom.    Resembles  an  impure  sand- 

stone whose  argillaceous  material  had 

been  altered  to  mica  during  the  meta- 

morphic  process  ;    crushes  to  a  sandy 

powder  like  a  sandstone. 

1  Carbonated. 

2  No.  17.  Analysis  (by  Strong):  SiOs,  49.15;  AljAt,  2L90 ;  FejOg,  6.60;  FeO,4.54;  CaO,  8.22;  MgO,  3.03;  NaaO.3.83; 
KjO,  1.61 ;  H20,  1.92 ;  100.80. 

»  No.  19.  Analysis  (Riggs,  Bull.  62,  p.  113) :  8iO2, 54.83 ;  A12O3, 25.49 ;  FejOg,  1.61 ;  FeO,  1.65  ;  CaO,  6.08 ;  MgO,  1.96 ; 
Na-jO,  5.69 ;  K»O,  1.87  ;  HSO,  i.18 ;  COo,  .18  ;  100.54. 

4  Nos.  19,  20,  and  21  were  collected  from  an  intrusion  of  granite-gneiss  into  greenstone,  which  has  been  called 
Upper  Huronian  by  Brooks,  the  granite-gneiss  being  placed  at  the  top  of  the  Upper  Huronian.    Bulletin  62,  p.  26. 
This  series  shows  a  gradation  from  massive  porphyritic  granite  to  very  fine-banded  gneiss.    No.  19  is  from  the  center 
of  the  intrusive  dike,  and  grades  almost  imperceptibly  on  both  sides  into  the  fine-grained  gneiss  of  which  No.  20  is  the 
type.    No.  21  is  similar  to  No.  20,  being  on  the  sides,  but  is  banded.    This  rock  is  more  basic  than  typical  granite, 
being  more  like  a  diorite  in  composition.    The  low  gas-volume  of  No.  20  in  comparison  with  the  two  other  speci- 
mens is  perhaps  to  be  explained  by  the  fact  that  it  is  a  much  more  porous  rock,  crumbling  readily  to  a  fine  powder 
on  the  anvil. 

5  Owing  to  an  accident  during  the  explosion  it  was  impossible  to  determine  the  relative  amounts  of  CH*,  H2,  and 
N2,  but  the  violence  of  the  explosion  suggests  that  there  was  little  Ng  present. 


16 


THE    GASES   IN    ROCKS. 


TABLE  8— Continued. 


Specimen  No.  and  remarks. 

P.ct. 
or  vol. 

H2S. 

C02. 

CO. 

CH4. 

B» 

N2. 

Total. 

132.  Olivine  free,  saussuratized  schistose  gab- 

P.ct 

0.07 

67.50 

1.95 

0.69 

28.71 

1.08 

100 

bro,  Menomlnee  district,  Lake  Superior 

Vol. 

.02 

20.07 

.58 

.20 

8.54 

.32 

29.73 

region.  Specimen  11166,  Slide  5747.  De- 

scribed by  Williams,  Bull.  62,  pp.  62-76. 
An  extremely  altered  gabbro,  contain- 

ing calcite,  sericite,  chlorite,  and  leu- 

coxene. 

33.  Laurentian   gneiss,    Marquette   district, 

P.ct. 

.07 

28.31 

5.07 

2.64 

59.66 

4.25 

100 

Mich.   Specimen  14718,  Slide  9361,  U.  S. 

Vol. 

.00 

.85 

.15 

.07 

1.79 

.12 

2.98 

G.  S.    From  C.  R.  Van  Hise. 

34.  Keewatin  greenstone,   Mesabi   district. 

P.ct 

.58 

62.38 

8.60 

.28 

31.38 

1.78 

100 

Oldest  known  series  of  the  Lake  Super- 

Vol. 

.19 

20.08 

1.16 

.09 

10.10 

.57 

32.19 

ior  region.  Specimen  40785,  Slide  15420, 
U.  S.  G.  8.     Considerable  water  was 

given  off  when  powder  was  heated. 

From  C.  R.  Van  Hise. 

35.  Keweenawan  diabase,  railroad  cut  south 

P.ct 

.45 

7.05 

1.57 

1.77 

87.66 

1.50 

100 

of  schoolhouse  in  Taylor's  Falls,  Minn. 

Vol. 

.01 

.25 

.06 

.06 

3.15 

.06 

3.59 

36.  Olivine  gabbro,  from  foot  of  cliff  at  NE. 

P.ct. 

.46 

19.97 

7.91 

3.96 

62.54 

5.16 

100 

headland  of  Beaver  Bay,  near  Duluth, 

Vol. 

.00 

.16 

.07 

.04 

.52 

.05 

.84 

Minn.  Specimen  4601,  Slide  4601,  U.S.G. 
S.  Collection  R.D.Irving.  (References: 

Mon.  v,  U.  S.  G.S.,  Lithol.,  pp.  37-45.  Lo- 

cation on  map,  p.  305  ;  description,  p.  309.  ) 
37.  Oglesby  blue  granite,  near  Elberton,  El- 

P.ct 

.07 

47.06 

4.74 

1.57 

44.33 

2.23 

100 

bert  Co.,  Ga.    From  S.  W.  McCallie. 

Vol. 

.00 

1.13 

.11 

.03 

1.06 

.05 

2.38 

38.  Stone  Mountain  granite,  Stone  Mountain, 
De  Kalb  Co.  ,  Ga.    From  S.  W.  McCallie. 

P.ct. 
Vol. 

.10 
.00 

10.93 
.08 

4.85 
.03 

1.55 
.01 

77.20 
.60 

5.37 
.04 

100 
.76 

39.  Coarse   reddish  Archean   granite,  Big 

P.ct. 

.11 

87.84 

3.51 

1.10 

3.61 

3.83 

100 

Stone  Lake,   near   Ortonville,   Minn. 

Vol. 

.00 

1.20 

.05 

.01 

.05 

.05 

1.36 

From  Blake  &  Co.     Microcline  and 

orthoclase  form  large  crystals  ;  quartz 

is  abundant,  but  biotite  is  rather  sparse. 

Described  in  Geol.  of  Minn.  ,  vol.  5,  p.  814. 

40.  Ortonville  granite,  biotite  crystals  of  last 
specimen  separated  from  quartz  and 
feldspar  by  mercuric  iodide  specific 

P.ct 
Vol. 

1.61 
.22 

92.40 
12.45 

1.71 
.23 

.45 

.06 

2.23 
.30 

1.60 
.21 

100 
13.47 

gravity  solution. 

1 

1 

1 

« 

Specimen  No.  and  remarks. 

S 

1 

I 

ir  dioxide 
l). 

1 

J_ 

1 

n 

f 

g 

1 

P 

1 

f| 
Si 

ii 

P 

>*  5 

i* 

m 

M 

W 

B 

1 

41.  Hamilton  shale,  Newsom's  Station, 

P.ct 

30.94 

21.17 

4.61 

4.29 

38.99 

100 

15  miles  W.  of  Nashville,  Tenn. 
From  Miss  Augusta  T.  Hasslock. 

Vol. 

29.38 

20.10 

4.38 

4.07 

37.03 

94.96 

An  exceedingly  bituminous  shale 

emitting  a  strong  odor  resembling 
that  of  asphalt  when  struck  with  a 

hammer.    What  part  of  this  gas 

really  existed  within  the  rock  in 

the  gaseous  state  can  not  be  stated  ; 

most  of  it  probably  came  from  de- 
composition of  organic  matter  pres- 
ent   Heavy  brown  tars  also  pro- 

duced.   No  determination  of  hy- 

drocarbon vapors  was  made. 

2  42.  Oil-rock  from  lead-zinc  mine  near 

P.ct 

6.79 

11.11 

18.12 

8.40 

4.00 

35.98 

13.18 

2.16 

100 

Platteville,  Wis.    From  H.  F.  Bain. 
«43.  Sillimanite  gneiss,  St.  Jean  de  Matha, 
Quebec.  From  F.  D.  Adams. 

Vol. 
P.ct 
Vol. 

3.90 

6.38 

54".74 
2.76 

10.43 
40.55 
2.05 

4.82 
1.64 
.09 

2.30 

20.67 
.61 
.03 

7.57 
1.10 
.05 

1.24 
1.36 
.07 

57.46 
100 
5.05 

1  No.  32.  Analysis :  8i02,  38.05 ;  A12O3,  24.73 ;  FeO,  5.65 ;  Fe»O,  6.08 ;  CaO,  1.25 ;  MgO,  11.58 ;  NajO,  2.54 ;  KnO,  1.94 ; 
HsO,  7.53 ;  CO»,  0.93 ;  100.28.     (R.  B.  Riggs,  Bull.  62,  p.  76.) 

2  Probably'only  a  small  part  of  gas  was  really  present  in  the  gaseous  condition,  the  analysis  being  made  to  show 
what  a  bituminous  shale  may  yield. 

8  A  metamorphosed  slate  of  the  Grenville  series.  Reference :  Am.  Jour.  ScL,  vol.  50,  p.  58.  Described  as  a  fine- 
grained garnetiferous  sillimanite  gneiss  containing  much  quartz  and  orthoclase.  Graphite  and  pyrite  also  present, 
causing  the  gneiss  to  weather  to  a  very  rusty  color.  Analysis  by  N.  N.  Evans,  of  McGill  University :  No.  43.  SiO2, 
61.96 ;  TiO2, 1.66 ;  AloOa,  19.73 ;  Fe,O8  and  FeO,  4.60 ;  FeSs,  4.33 ;  MnO,  trace ;  CaO,  0.35 ;  MgO,  1.81 ;  NajO,  0.79 ;  K20, 
2.50;  H20  (ignition)^  L82;  99.55. 


THE    ANALYSES. 
TABLE  8— Continued. 


17 


1 

| 

g 

Specimen  No.  and  remarks. 

| 

I 

1. 

1 

1 

g 

I 

a 

I 

P 

i~ 

£ 

1 

1 

1 

I 

44.  Nephelite  syenite,  north  of  Mountain  Lake, 

P.ct. 

42.42 

8.76 

5.49 

36.33 

7.00 

100 

Tp.  of  Methuen,  Ontario.    F.  D.  Adams. 

Vol. 

.29 

.05 

.04 

.25 

.05 

.63 

Or  igneous  origin. 

45.  Iron-bearing  basalt,  Ovifak,  Disco  Island, 

P.ct. 

0.03 

46.50 

21.63 

2.09 

27.88 

1.87 

100 

Greenland. 

Vol. 

.00 

3.74 

1.74 

.17 

2.24 

.16 

8.05 

46.  Magnetite  sand,  Snake  River  bed,  Idaho, 
from  Oskar  Eckstein.     Separated  from 

P.ct. 
Vol. 

83.91 
2.22 

10.19 

.27 

5.90 
.16 

100 
2.65 

impurities  by  magnet. 

47.  Andesite,  Red  Mountain,  NW.  of  San  Fran- 
cisco Peaks,  Ariz.    Collected  by  W.  W. 

P.ct. 
Vol. 

.01 
.00 

80.38 
5.12 

9.02 
.57 

4.74 
.30 

1.84 
.12 

4.03 
.26 

100 
6.37 

Atwood.     Mr.   Arthur  Taylor  describes 

this  rock  as  an  andesite  porphyry  whose 

ground-mass  (96  p.  ct.  of  the  whole)  con- 
sists of  48  p.  ct.  pyroxene,  31  p.  ct.  plagio- 

clase  (labradorite),   and  12  p.  ct.  mag- 

netite.   The   phenocrysts  are  lime-soda 
feldspar,  augite,  hornblende,  and  mag- 

netite.    Occurs  as  irregular  blocks  ce- 

mented in  the  tuff  or  volcanic  breccia  of 

which  Red  Mountain  is  built. 

48.  Pyroxene  crystals,    Red  Mountain,   Ariz. 

P.ct. 

8.90 

62.62 

14.46 

1.30 

7.01 

5.71 

100 

Collected    by   W.    W.    Atwood.     These 

Vol. 

.10 

.69 

.16 

.01 

.08 

.06 

1.10 

crystals,  ranging  in  size  from  a  bean  to  a 

small  marble,  were  found  loose  on  the 

surface,  having  weathered  out  of  the 

breccia. 

49.  Rhyolite  vitrophyre,  ridge  N.  of  Park  Basin, 
Telluride  Quadrangle,  Colo.     Specimen 

P.ct. 
Vol. 

92.66 
2.33 

1.94 
.05 

1.39 
.03 

2.71 
.07 

1.30 
.03 

"I* 

No.  3054  U.  S.  G.  S.    A  lava  flow  belong- 

ing to  the   intermediate  series.    From 

Whitman  Cross. 

50.  Nephelite  melilite  basalt,  Uvalde  Quadran- 
gle, Tex.    Collected  by  T.  W.  Vaughan. 
Described  (Uvalde  Folio,  p.  4)  as  a  very 

P.ct. 
Vol. 

1.99 
.05 

40.32 
1.07 

7.55 
.20 

2.18 
.06 

44.18 
1.16 

8.78 
.10 

100 
2.64 

fine-grained,  dark-colored  rock,  with  the 

nephelite  invisible   to  the  naked  eye. 

Contains  little  or  no  feldspar  and  com- 
paratively little  nepheline.    Olivine  and 

augite  are  the  most  important  constitu- 

ents.   The  presence  of  melilite  indicates 
unusual  amount  of  lime  in  magma.    Age 

doubtfully  placed  as  Eocene. 
51.  Shonkinite,  Highwood  Mountains,  Mont. 
Core  rock  of  Shonkin  stock.    Described 

P.ct. 
Vol. 

.04 
.00 

8.85 
.11 

4.97 
.06 

3.94 
.05 

78.08 
.95 

4.12 
.05 

100 
1.22 

(Ft.  Benton  Folio,  p.  3)  as  a  rock  of  the 

syenite  family  very  rich  in  augite,  con- 

taining accessory  oli  vine  and  black  mica. 
While  the  chief  light-colored  constituent 

Is  orthoclase,  nephelite  and  sodalite  are 

present  in  varying  amounts.    An  intru- 

sive of  probably  Eocene  age.    Collected 
by  W.  H.  Weed. 

52.  Theralite,  from  the  laccolites  on  Upper 
Shield   River   Basin,   Crazy  Mountains, 
Mont.  U.  S.  National  Museum  No.  73138. 

P.ct. 
Vol. 

.01 
.00 

48.18 
1.08 

7.63 
.17 

1.58 
.04 

41.21 
.93 

1.39 
.03 

100 
2.25 

Collected  by  W.  H.  Weed.     Described 

(Little  Belt  Mountains  Folio,  p.  4)  as  a 

dark-gray  basaltic  rock  commonly  occur- 

ring in  sheets,  but  rarely  in  dikes.    Por- 
phyritic  crystals  of  augite  form  the  most 

prominent    phenocrysts,    though    large 
plates  of  brown  mica  are  common.    Col- 
orless part  of  the  ground-mass  is  a  granu- 
lar mixture  of  nephelite  and  lime-soda 

feldspars.    Eocene  age. 
53.  Quartz  syenite  porphyry,  summit  of  En- 
gineer Mountain,  Silverton  Quadrangle, 

P.ct. 
Vol. 

(') 

24.89 
.11 

17.22 
.08 

50.22 
.22 

7.53 
.03 

100 
.44 

Colo.    No.  3728  U.   S.  G.  S.     From  Dr. 

Cross.    Described  (Silverton  Folio,  p.  11) 

as  strongly  porphyritic,  with  many  glassy 
orthoclase  crystals  colored  reddish  by  fine 

'  Carbonated. 


18 


THE    GASES   IN    ROCKS. 


TABLE  8— Continued. 


Specimen  No.  and  remarks. 

P.ct. 
or  vol 

3. 

( 

CO. 

CH< 

^ 

I 

I* 

N2. 

Total. 

ferritic  pigment.     Also  phenocrysts  of 
quartz,   plagioclase,  biotite,  and  horn- 

blende;    dark,    ash-gray  ground-mass. 
Either  an  intrusive  or  resting  upon  andes- 
itic  tuffs  of  Silverton  series. 

54.  Altered  Jurassic  shale,  LaPlata  Quadrangle, 
Colo.    Contact  zone  below  Indian  Trail 

P.ct. 
Vol. 

0.1 

.0 

6 

0 

P) 

22.09 
.15 

5.41 
.W 

65 

96 
45 

6.38 
.04 

100 

Ridge.    Alteration  due  to  intrusion  of 

vogesite.    (See  analysis  No.  84.)    From 

Dr.  Cross. 

55.  Garnetiferous  gneiss,  Darwin's  Falls,  Tp. 

P.ct. 

13.2 

7 

ft 

X26 

9.51 

2.11 

52 

M 

2.65 

100 

of  Rawdon,  Quebec.    Probably  of  sedi- 

Vol. 

.1 

1 

.16 

.07 

.(K 

41 

.02 

.79 

mentary  origin.    From  F.  D.  Adams. 

56.  Hornblende  syenite,  Cape  Elizabeth,  Me. 

P.ct. 

.0 

3 

5.13 

2.76 

l.OS 

88 

77 

1.28 

100 

From  the  drift.  U.  S.  N.  M.  No.  39035. 

Vol. 

.0 

0 

.16 

.07 

.OS 

2 

22 

.03 

2.50 

57.  Granite  porphyry  bowlder,  northern  New 

P.ct. 

3.3 

5 

t1) 

22.19 

1.7E 

69 

37 

3.34 

100 

York. 

Vol. 

.0 

4 

.27 

.05 

85 

.04 

1.22 

58.  Intrusive  in  Highwood  Mountains,  E.  side 

P.ct. 

3 

8.44 

4.44 

51 

25 

3.96 

100 

of  divide,  Highwood  Gap,  Ft.  Benton 

Vol. 

.07 

M 

45 

.03 

.87 

Quadrangle,  Mont.    Microscopically  re- 
sembles a  diorite;  probably  of  Eocene 
age.    Collected  by  W.  H.  Weed. 

259.  Nevadite,  Chalk  Mountains,  Ten-mile  dis- 

P.ct. 

5 

M9 

19.29 

4.7C 

7 

JH 

11.28 

100 

trict,  Colo.    From  U.  S.  Nat.  Mus.    De- 

Vol. 

.15 

.06 

.01 

02 

.03 

.27 

scribed  in  Monograph  xu,  p.  345.     Con- 

tains numerous  dark  quartz  crystals  and 

clear  sanidines,  embedded  in  a  light  gray 
ground-mass  made  up  of  sanidine,  plag- 
ioclase, and  quartz,  but  containing  little 

biotite  or  magnetite. 

j 

t 

g 

| 

. 

1 

| 

1 

i 

x. 

Specimen  No.  and  remarks. 

o 

'•5 

1 

S 

| 

A 

^  . 

I 

ll 

I 

1 

|| 

ll 

J| 

I 

1 

I 

J 

1 

w~ 

£ 

w"2 

3~ 

1 

H 

6 

1 

60.  Diorite  plug  in  Cretaceous  shales,  between 

P.ct. 

2.06 

0.16 

14.55 

4.18 

3 

41 

71.3 

7 

4.27 

100 

forks  of  Deep  Creek  on  ridge  from  Mt. 

Vol. 

.03 

.00 

.22 

.06 

05 

1.1 

0 

.06 

1.52 

Ruffner,  3  miles  from  lower  contact,  Tell- 

uride  Quadrangle,  Colo.     No.  2872  U.  8. 

G.  S.    From  Whitman  Cross. 

61.  Diabase,  Nahant,  Mass  

P.ct. 

2.18 

56.53 

2.36 

1 

36 

35.9 

3 

1.64 

100 

Vol. 

.19 

4.91 

.21 

12 

3.1 

i 

.15 

8.71 

62.  Andesite,  Rosita  Hills,  Ouster  Co.,  Colo., 
from  summit  of  small  hill  east  of  spring 

P.ct. 
Vol. 

.06 
.00 

.... 

P) 

35.67 
.27 

6 

67 
05 

40.0 

J 

2 
0 

17.58 
.13 

100 
.75 

on  Rosita  Road.    Dike  facies  of  Prmgle 

type.     (See  report  on  Geology  of  Silver 
Cliff,  Rosita  Hffisarea,  by  Whitman  Cross.  ) 

63.  Anorthosite,  sheared  igneous  rock,  2.5  miles 
from  Chertsey,  Quebec.    F.  D.  Adams. 
64.  Andesite  Lipari  Islands 

P.ct. 
Vol. 
P  ct 

.02 
.00 
06 

71.99 
2.36 
7029 

8.40 
.27 
4.85 

54 
02 
9g 

17.1 

.5 
21  t 

1 

6 

2 

1.88 
.06 
2.20 

100 
3.27 
100 

Vol. 

.00 

.56 

.04 

01 

4 

7 

.02 

.80 

65.  Fine-grained  gneiss,  lot  5,  Concession   I, 

P.ct. 

85 

12 

13.89 

0. 

39 

100 

Harburn  Tp.,  Ontario.     Dr.  Adams  re- 

Vol. 

4 

15 

.68 

. 

35 

4.88 

gards  this  as  almost  certainly  an  altered 

sediment,  for  it  occurs  in  beds  interstrati- 

fied  with  limestone.    Impregnated  with 

pyrite  and  contains  graphite.    Analysis 
shows  it  to  be  a  tehamose. 

66.  Gneiss  of    igneous  origin,  lot  28,  R.  9, 

P  ct 

04 

1935 

891 

2 

20 

64.2 

1 

5.26 

100 

Wollaston  Tp.,  Ontario.     F.  D.  Adams. 

Vol. 

.00 

.28 

.13 

03 

') 

.08 

1.47 

67.  Feather  amphibolite,  lot  16,  R.  12,  Wollas- 

P.ct. 

.22 

(*) 

54.45 

* 

89 

35  j 

2 

6.82 

100 

ton  Tp.,  Ontario.    Probably  of  sedimen- 

Vol. 

.00 

.49 

03 

.3 

2 

.06 

.90 

tary  origin.    F.  D.  Adams. 

1  Carbonated. 

2  No.  59.    Analysis  (p.  589)  :  SiOs,  74.45; 
sO,  3.97  ;  HSO,  0.66  ;  P205,  0.01  ;  100.38. 


14.72;  FeO,  0.56;  MnO,  0.28;  CaO,  0.38;  MgO,  0.37;  K2O,  4.53; 


THE    ANALYSES. 


19 


TABLE  8 — Continued. 


d 

•3 

! 

I 
i 

1 

1 

R 

!$ 

<$ 

Specimen  No.  and  remarks. 

§ 

_0 

0 

O 

T" 

5, 

d" 

•3  • 

3 

1 
1 

P 

Carbon 
(C02) 

f- 

1 

H 

I 

| 

I 

68.  Amphibolite,  Maxwell's  Crossing,  Glamor- 
gan Tp.,  Ontario.    A  highly  altered  lime- 

P.ct. 
Vol. 

0.06 
.00 

« 

10.94 
.26 

2.11 
.05 

84.01 
2.01 

2.88 
.06 

100 
2  38 

stone.    Dr.  Adams. 

69.  Rice  rock,  Canadian  Pacific  R.  R.  0.25  mile 

P.ct. 

4.86 

14.67 

5.14 

1.45 

71.89 

1.99 

100 

east  of  Sudbury,  Ontario.     Probably  an 

Vol. 

.16 

.47 

.16 

.05 

2.32 

.06 

3.22 

altered  sediment  of  Huronian  age.    Dr. 

Adams. 

70.  Andesite,    Granite    Mountain,    Iron    Co., 

P.ct 

.03 

77.50 

4.75 

.95 

15.35 

1.42 

100 

Utah.  A  laccolite  in  Paleozoic  sediments. 

Vol. 

.00 

2.66 

.16 

.03 

.53 

.05 

3.43 

C.  K.  Leith. 

71.  Vein  quartz,  Granite  Mountain,  Iron  Co., 

P.ct. 

13.93 

11.26 

4.00 

64.40 

6.41 

100 

Utah.    Associated  with  iron  ore  which 

Vol. 

.11 

.09 

.03 

.53 

.05 

.81 

has  developed  along  the  contact  of  the 
laccolite  and  intruded  limestone.  Accord- 

ing to  Leith  it  was  presumably  derived 

from  the  andesite  (No.  70). 

72.  Phonolite  trachyte,  east  part  of  Bull  Moun- 
tain, Pike's  Peak  Quadrangle,  Colo.    No. 
2488U.S.G.S.  Described  by  Cross  (Pike's 

P.ct. 
Vol. 

.27 
.00 

69.37 
.76 

4.85 
.05 

2.67 
.03 

17.16 
.19 

5.69 
.06 

100 
1.08 

Peak  Folio,  p.  3)  as  a  dense,  grayish-green 

rock  with  tabular  crystals  of  sanidine, 

which  give  it  a  typical  porphyritic  tex- 

ture. 

73.  Coarse  diorite  bowlder  from  Bluehill  sheet, 

P.ct 

3.28 

14.99 

3.78 

2.00 

72.83 

3.12 

100 

Penobscot  Bay  Quadrangle,  Me.     From 

Vol. 

.06 

.27 

.07 

.04 

1.29 

.05 

1.78 

E.  8.  Bastin. 

74.  Diorite,  Deer  Isle  sheet,    Penobscot  Bay 

P.ct 

1.44 

4.65 

.78 

4.38 

85.62 

3.13 

100 

Quadrangle,  Me.    No.  1157.    From  E.  S. 

Vol. 

.07 

.21 

.04 

.20 

3.95 

.14 

4.61 

Bastin. 

75.  Potsdam  sandstone,  upper  narrows  of  the 
Bamboo,  Ablemans,  Wis.     Hard,  indu- 

P.ct 
Vol. 

.15 
.00 

27.29 
.09 

15.12 
.05 

5.88 
.02 

37.86 
.13 

13.70 
.05 

100 
.34 

rated  white  sandstone,  not  far  from  the 

contact  with  the  quartzite. 

2  76.  Potsdam  sandstone,  Ablemans,  Wis  

P.ct. 

.08 

9.67 

15.42 

3.70 

52.11 

19.02 

100 

Vol. 

.05 

.07 

.02 

.23 

.08 

.45 

77.  Huronian  quartzite,  South  Range,  near  Bar- 

P.ct. 

'  '.is 

25.12 

9.53 

2.71 

55.43 

7.08 

100 

aboo,  Wis. 

Vol. 

.00 

.11 

.04 

.01 

.24 

.03 

.43 

78.  Permian   red   sandstone,   Garden  of    the 

P.  ct. 

.05 

0) 

60.69 

6.27 

27.28 

5.71 

100 

Gods,  near  Colorado  City,  Colo. 
79.  Topaz    quartz-porphyry,    Schneckenstein, 
near  Auerbacn,  Saxony. 

Vol. 
P.ct 
Vol. 

.00 
trace 
.00 

33.41 
.32 

.71 
8.16 
.08 

.07 
4.87 
.05 

.32 
45.40 
.44 

.06 
8.15 
.08 

1.16 
100 

.97 

80.  St.  Peter  sandstone,  Minnehaha  Creek,  be- 

P.ct. 

2.6 

56.5 

9.6 

15.7 

1.7 

13.9 

100 

low  the  falls,  Minneapolis,  Minn.    A  soft, 
remarkably  white,  coarse-grained  sand- 

Vol. 

.00 

.02 

.00 

.01 

.00 

.01 

.... 

.04 

stone.    Before  heating  in  the  tube  the 

grains  were  washed  with  dilute  HC1. 

81.  St.  Peter  sandstone,  Minnehaha.    The  sand 

P.ct 

6.40 

13.73 

2.41 

35.19 

42.27 

100 

No.  80,  pulverized  and  heated  a  second 

Vol. 

.03 

.07 

.01 

.17 

.21 

.49 

time. 

82.  Quartzite  belonging  to  Grenville  Series, 
Darwin's  Falls,  Rawdon   Tp.,  Quebec. 

P.ct. 
Vol. 

37.65 
.23 

35.05 
.21 

7.12 
.04 

2.31 
.01 

15.60 
.09 

2.27 
.01 

100 
.59 

From  F.  D.  Adams. 

83.  Quartz  crystals,  Lincoln  Co.,  N.  C.    Beauti- 
ful crystals  whose  perfectly  formed  faces 
indicated  that  they  were  formed  from 

P.ct. 
Vol. 

1.7 
.00 

30.0 
.03 

7.2 
.00 

6.4 
.00 

14.4 
.01 

35.1 
.03 

5.2 
.00 

100 
.08 

aqueous  solution.    Entirely  transparent 

and  without  visible  inclusions. 

384.  Vogesite,  Indian    Trail    Ridge,    La   Plata 
Quadrangle,  Colo,  (a  sheet  in  the  Gunni- 

P.ct. 
Vol. 

Undet 

W 

10.58 
.14 

2.48 
.03 

82.53 
1.08 

4.41 
.05 

100 
1.30 

son  shales)  .   A  fine-grained  greenish  rock 
containing  about  equal  amount  of  feld- 
spars and  femic  minerals,  and  more  augite 
than  hornblende  ;  feldspars  much  serici- 

tized  and  obscured  by  chlorite,  epidote, 
and  calcite.    Described  in  La  Plata  Folio, 
p.  7.  From  Dr.  Cross.  Allied  type  analyzed 

by  W.  F.  HUlebrand. 

i  Carbonated. 

» The  identical  sand  used  in  No.  75,  powdered,  and  heated  a  second  time.  This  experiment  was  to  determine 
whether  gas  which  was  unable  to  escape  might  not  still  remain  within  the  sand  grains.  As  this  powder  yielded 
more  gas  than  the  fresh  sand,  most  of  the  gas  in  the  first  trial  apparently  came  from  the  surface  or  near  the  surface 

°f  ^No^^Analysis:  SiO2,  43.98;  A1203, 13.30;  FeoO3, 3.67  ;  FeO,  6.92 ;  MgO,  7.03;  CaO,  10.66;  Na.A2.15;  K20,1.64; 
H20, 1.94  ;  TiO2, 1.18 ;  C02,  6.46 ;  P2O6,  .32 ;  FeSj,,  .54 ;  etc.  .36 ;  100.15. 


20 


THE    GASES   IN   ROCKS. 


TABLE  8— Continued. 


, 
Specimen  No.  and  remarks. 

P.ct. 
or  vol. 

H2v 

3. 

cc 

fr 

o 

). 

C 

H4. 

Hs. 

K, 

02. 

Total. 

85.  Keweenawan  diabase;   drill  core  from 

P.ct. 

.( 

3 

33. 

n 

2 

40 

.35 

60.24 

1.37 

100 

Franklin  Junior  Hole  No.  3,  near  Hough- 

Vol. 

.C 

K) 

1. 

» 

09 

.09 

2.34 

.05 

3.88 

ton,    Mich.     From   A.  C.   Lane.     This 

piece  came  from  a  depth  of  524  feet,  meas- 
ured along  a  line  48°  from  the  horizontal. 
Overlaying  drift  amounts  to  110  feet,  so 
that  the  preglacial  covering  of  specimen 
was  in  the  neighborhood  of  315  feet,  plus 

thickness  of  rock  removed  by  glaciers. 

This  specimen  is  from  a  massive  flow  of 

ophite,  62  feet  in  thickness. 

186.  Diabase,  Nahant,  Mass.  Material  from  same 

P.ct. 

.( 

U 

61. 

25 

2 

47 

"1 

.32 

33.69 

1.23 

100 

specimen  as  No.  61. 

Vol. 

.( 

K) 

8. 

51 

84 

.18 

4.68 

.17 

13.88 

287.  Diabase,  Nahant,  Mass.  Material  from  same 

P.ct. 

25. 

>:\ 

20 

15 

< 

.36 

21.21 

27.05 

100 

specimen  as  No.  86. 
«88.  Diabase,  Nahant,  Mass.  Material  from  same 
specimen  as  Nos.  86  and  87. 

Vol. 
P.ct. 
Vol. 

is.; 

• 

,0 
1 

•     j 
38. 

06 
19 
•>2 

9 

05 
01 
14 

: 

.01 
.95 
.06 

.05 
33.80 
.54 

.06 
1.75 
.03 

100 
1.60 

89.  Albite  crystals,  Hebron,  Maine  

P.ct. 

Vol. 

17! 

09 

14 

06 

< 

>.80 

49.95 

12.10 

100 

90.  Wollastonite,  Harrisville,  Lewis  Co.,  N.  Y. 

P.ct. 

«"'. 

13 

~6 

77 

'.85 

2.16 

3.09 

ioo  " 

Taken  from  a  large  specimen  of  pure- 

Vol. 

2. 

37 

18 

.02 

.06 

.08 

2.71 

white  wollastonite  and  reduced  to  a  pow- 
der in  an  agate  mortar.   No  suggestion  of 
any  iron.    Acid  liberated  very  little  car- 

bon dioxide  from  powder.   Walker  Muse- 

um Collection. 

91.  Andesite,  summit  of  Mt.  Orizaba,  Mexico, 
18,300  ft.  altitude.  Unquestionably  a  lava, 

P.ct. 
Vol. 

• 

67. 

07 
22 

16 

28 
05 

J.46 
.00 

3.94 
.01 

10.25 
.03 

100 
.31 

and  not  a  tuff,  somewhat  porous,  giving 

off  bubbles  when  immersed  in  water. 

«92.  Amphibolite,  Chester,  Mass.  A  very  coarse- 
grained specimen.    Walker  Museum. 

P.ct. 
Vol. 

... 

- 

36. 

2 

59 
20 

17 

1 

13 

05 

: 

L.57 
.09 

42.93 
2.59 

1.78 
.10 

100 
6.03 

*92a.  As  the  gas  was  still  coming  off  slowly  at 
the  end  of  5  hours,  the  same  material  was 

P.ct. 
Vol. 

7. 

V, 
03 

u 

65 
.05 

1.62 
.01 

66.% 
.25 

7.22 
.03 

100 
.37 

heated  the  next  day  for  an  additional  3J 

hours. 

d 

S 

i 

1 

j 

1 

. 

I 

1 

] 

= 

£ 

w" 

3 

"«" 

Specimen  No.  and  remarks. 

g 

a 

.; 
1C 

_ 

I 

^ 

•^ 

S 

I 

IS 

$ 
X 

1 

1 

§: 

A 

1» 

1 

1 

a 

i 

2 

w 

5 

6 

M 

% 

w 

o 

93.  Pitchblende,   Beaver  Co.,   Colo.     From 

P.ct. 

6) 

( 

) 

23. 

)i 

2.57 

7.16 

27.85 

38.48 

100 

H.  N.  McCoy. 

Vol. 

,i 

.03 

.07 

.27 

.37 

.98 

?94.  Carnotite,  Colorado,  from  H.  N.  McCoy. 
Uranyl  vanadate,  probably  with  some 
radium. 

P.ct.  1 
Vol. 

race 
0.00 

81 
2 

31 
46 

?! 

i 

a 

.71 
.02 

1.48 
.05 

7.48 
.22 

1.28 
.04 

100 
3.02 

95.  Greenalite  rock,  Biwabik  formation,  Mesa- 

P.ct. 

.17 

7 

02 

4j 

3 

.04 

86.28 

2.46 

100 

bi  district,  Minn.    No.  45759  U.  S.  G.  S. 

Vol. 

.01 

42 

!4 

.00 

5.18 

.14 

5.99 

From  C.  K.  Leith. 

96.  Grimerite  rock,  Mesabi  district,  Minn.    A 

P.ct. 

.68 

37 

97 

8.1 

>7 

.78 

45.78 

6.22 

100 

ferruginous  chert.    No.  45113  U.  8.  G.  S. 

Vol. 

.02 

1 

14 

6 

.02 

1.39 

.19 

3.02 

From  Dr.  Leith. 

97.  Micaceous  quartzite,  Uinta   Mts.,   Utah. 

P.ct. 

.36 

•10 

44 

8.f 

2 

2.46 

43.93 

4.19 

100 

From  Dr.  Leith. 

Vol. 

.01 

57 

.] 

2 

.03 

.63 

'    .06 

1.42 

1  In  order  to  see  whether  the  methane  came  from  hydrocarbons  soluble  in  alcohol  or  ether,  this  material,  after 
being  very  finely  pulverized,  was  digested  with  alcohol  (free  from  organic  impurities)  for  20  hours ;  then  with  fat- 
free  ether  for  45  hours.    It  was  then  thoroughly  washed  with  ether  on  a  filter  which  had  previously  been  treated 
with  the  same  fat-free  ether.    Afterwards  dried  at  100°  in  an  oven. 

2  To  get  rid  of  all  carbonates  the  powder  was  treated  with  concentrated  nitric  acid  for  66  hours.    Much  gas  was 
given  oft,  including  a  copious  evolution  of  nitric  oxide.    The  powder  was  washed  until  all  traces  of  acid  were  re- 
moved, after  which  it  was  dried  in  an  air-bath  at  115°.    This  material  heated  then  gave  No.  87. 

8  Treated  with  dilute  sulphuric  acid  for  three  days  in  a  vacuum.  The  powder  was  washed  on  a  filter  until  the 
filtrate  was  no  longer  made  turbid  by  barium  chloride,  and  then  dried  in  an  oven  and  heated  in  an  air-bath  at  125° 
for  over  an  hour. 

4  Nos.  92  and  92a.    A  perfect  vacuum  was  maintained  between  these  two  combustions. 

6  Sulphate. 

>  Carbonated. 


7  The  high  percentage  of  nitrogen 
afterwards  during  the  S] 


uum  for  days  f 

brilliantly,  but  no  argon  lines  coul 


;en  shown  in  this  analysis  is  not  due  to  leakage  of  air,  for  the  pump  held  its  vac- 
e  spectroscopic  examinations.  The  yellow  helium  line,  D8  (A=  5876)  stood  forth 
d  be  seen  in  the  spectrum. 


THE    ANALYSES. 


21 


TABLE  8 — Continued. 


Specimen  No.  and  remarks. 

P.ct. 
or  vol. 

H*. 

S02. 

C02. 

CO. 

CH,. 

H* 

N, 

NH3. 

Total. 

98.  Quartzite,  Rib  Hill,  near  Wausau,  Wis. 

P.ct. 

0.52 

68.15 

6.87 

2.52 

19.53 

2.41 

100 

From   Samuel  Weidman.    Famous  for 

Vol. 

.01 

.62 

.06 

.02 

.17 

.02 

.90 

its  gas  bubbles.    Powdered  on  an  an- 

vil and  metallic  iron  thus  introduced 

removed  as  completely  as  possible  with 

a  magnet. 

199.  Quartzite,  Rib  Hill,  Wis.    Same  epecimen 

P.ct. 

.17 

96.69 

.96 

.23 

1.39 

.56 

100 

as  No.  98.    Granules  used  instead  of  fine 

Vol. 

.00 

.86 

.01 

.00 

.02 

.00 

.89 

powder.  Crumbles  readily  into  granules, 

which  were  treated  with  boiling  hy- 

drochloric  acid  to  remove   any    iron 

which  might  have  come  from  the  anvil. 

100.  Auriferous,  pyritiferous  quartz,  Cargo,  near 
Orange,  New  South  Wales.  No.  837  N.  S. 

P.ct. 
Vol. 

1.07 
.01 

75.54 
.66 

3.36 
.03 

3.99 
.04 

13.57 
.12 

2.47 
.02 

100 
.88 

W.;  No.  3150  U.  of  W.     Dr.  Leith.    Re- 

duced to  a  coarse  powder  on  an  anvil 

and  treated  with  boiling  dilute  hydro- 

chloric acid  which  removed  any  iron  in- 
troduced. After  being  carefully  washed 

and  dried  it  was  more  finely  reduced  in  a 

porcelain  mortar. 

101.  Beryl  from  pegmatite  dike,  New  England. 
Walker  Museum   Collection.    Material 

P.ct. 
Vol. 

.34 
.00 

.... 

35.05 
.15 

3.37 
.01 

1.37 
.00 

55.83 
.24 

4.04 
.02 

100 
.42 

for  this  analysis  taken  from  a  massive 

beryl,  8  inches  in  diameter,  as  transpar- 
ent as  window-glass  and  without  visible 

inclusions  or  impurities.    Instead  of  be- 

ing pulverized  the  material  was  used  in 
the  form  of  small  fragments  which  were 

washed  with  boiling  hydrochloric  acid. 

After  heating,  the  transparent  frag- 

ments became  white  and  opaque,  resem- 
bling porcelain. 

lOla.  As  7J  hours  failed  to  expel  all  the  gas, 

P.ct. 

10.0 

2.2 

5.6 

76.9 

53 

100 

the  vacuum  was  maintained  overnight, 

Vol. 

.01 

.00 

.00 

.07 

.00 

.08 

and  the  material  heated  4  hours  more 

next  day. 

102.  Pegmatite,  containing  many  crystals  of 

P.ct. 

.04 

3.70 

3.53 

3.03 

87.21 

2.42 

0.07 

100 

tourmaline,  Chesterfield,  Mass.   Walker 

Vol. 

.00 

.06 

.06 

.05 

1.45 

.04 

.00 

1.66 

Museum. 

103.  Quartz  from  pegmatite  vein,  Jones  Falls, 
Baltimore,  Md.    No.  2211,  Univ.  of  Wis. 

P.ct. 
Vol. 

68.4 
.09 

13.9 
.02 

2.9 
.00 

7.4 
.01 

7.4 
.01 

100 
.13 

collection.    Dr.  Leith.    Specimen   con- 

tained a  large  crystal  of  microcline  over 
2  niches  in  length,  indicating  conditions 

favorable  to  crystallization.    No  micro- 

cline was  used  for  the  analysis,  however. 

If  pegmatites  contain  much  gas,  it  was 
thought  this  one  should  yield  a  good 

volume. 

104.  Albite,  Gibb's  mica  mine,  Yancey  Co.,  N. 

P.ct. 



9.3 

11.3 

19.6 

59.8 





100 

C.    Walker  Museum. 

Vol. 

.00 

.01 

.02 

.04 

.07 

105.  Quartz  from  Miocene  lava,  Iron  Co.,  Utah. 
No.  46614  U.  S.  G.  S.    From  E.  C.  Harder. 

P.ct. 
Vol. 

.22 
.00 

:::: 

57.71 
.12 

27.12 
.06 

2.32 
.00 

12.63 
.03 

100 
.20 

2  106.  Allegan  meteorite,  a  stony  aerolite  which 
fell  at  Allegan.  Mich.,  July  10,  1899,  and 
was  dug  out  of  the  sand  still  hot,  within 

P.ct. 
Vol. 

trace 
.00 

41.74 
.21 

38.61 
.19 

'2.92 
.01 

16.73 
.08 

.00 
.00 

100 
.49 

6   minutes    of    its  fall.      From  U.  S. 

National  Museum  through  G.  P.  Mer- 

rill.   Described  by  Merrill  and  Stokes 

(Proc.  Washington  Academy  of  Sciences, 
vol.  2,  pp.  41-68).     Before  extracting 
the  gas,  the  powdered  meteoric  material 

was  heated  in  a  vacuum  at  150°  for  3 

hours  in  the  presence  of  phosphorus 

pentoxide.   Apparatus  was  then  allowed 
to  stand  for  20  hours  to  enable  the  dry- 

ing agent  to  absorb  all  moisture  not 

chemically  combined. 

N 

»The  volume  of  carbon  dioxide  being  much  greater  in  the  case  of  the  granules  than  in  the  finely  reduced 
powder  strongly  suggests  that  much  of  this  gas  is  mechanically  inclosed  in  cavities  within  the  quartzite,  and 

escapes  when  the  granules  are  pulverized.  "This  opinion  was" strengthened  by  a  slight  cracking  noise  which 
came  from  within  the  tube  as  soon  as  heat  was  applied.  The  gas  came  off  with  a  rush  when  the  tube  was  heated. 
2  No.  106.  Chemical  analysis  by  Dr.  H.  N.  Stokes :  Metallic  part,  23.06  per  cent,  as  follows :  Fe,  21.09;  Cu,  .01 ; 
Ni,  1.81 ;  Co,  .15.  Stony  part,  76.94  per  cent.,  as  follows  :  SiO.>,  34.95 ;  TiO»,  .08 ;  P206,  .27  ;  A12O3,  2.55 ;  Cr2O3,  .53  ;  FeO, 
8.47 ;  FeS,  5.05 ;  MnO,  .18 ;  CaO,  1.73 ;  MgO,  21.99 ;  K^O,  .23 ;  NajO,  .66 ;  H20  at  110°,  .06 ;  above  110°,  .19 ;  100.00. 


22 


THE    GASES   IN    ROCKS. 


TABLE  8 — Concluded. 


Specimen  No.  and  remarks. 

P.ct. 
or  vol. 

HjS. 

S02. 

C02. 

CO. 

CH4. 

H2. 

No. 

NH8. 

Total. 

UO?.  Estacado  meteorite,  fell  near  Estacado, 

P.ct. 

0.39 

28.47 

29.31 

3.39 

36.25 

1.69 

100 

Tex.  ,  in  1882.  Described  by  K.  S.  Howard 

Vol. 

.00 

.24 

.03 

.31 

.01 

.84 

(Am.  Jour.  Sci.,  vol.  22  (1906),  pp.  55-60). 
Kept  in  a  vacuum  at  ordinary  tempera- 
ture with  phosphorus  pentoxide  for  66 
hours  ;  then  heated  at  150°  for  5  hours, 
and  allowed  to  remain  in  vacuo  for  19 

hours  more,  before  attempting  to  extract 

8108.  Toluca  meteorite,  a  medium  octahedrite 

from  Toluca,  Mexico. 
3First  determination  

P.ct. 

.02 

43.29 

35.48 

1.44 

17.84 

1.93 

100 

Vol. 

.00 

10.57 

8.67 

.35 

4.36 

.47 

24.42 

*  Second  determination 

P  Ct. 

10 

53.99 

1.91 

18  49 

3  19 

100 

Vol. 

!oi 

O'OK 

5*45 

1.87 

.32 

1009 

6Third  determination  

P.ct. 

.13 

e!40 

71.05 

2i35 

14.54 

5.53 

100 

Vol. 

.00 

.12 

1.32 

.04 

.27 

.10 

1.85 

6  109   Iron  ore  Iron  Co   Utah  No          U  S  G  S 

From  C.  K.  Leit'h.    Chiefly  limonite  and 

magnetite,  with  some  iron  carbonate 

and  sulphate: 

First  portion  (gas  which  came  off  in 

P.ct. 

51.35 

20.62 

27.35 

.68 

100 

20  minutes). 

Vol. 

11.55 

4.64 

6.15 

.15 

22.49 

Second  portion  (gas  which  came  off  in 
the  next  40  minutes). 

P.ct. 

Vol. 

48.75 
10.65 

20.43 
4.47 

30.12 
6.58 

.03 
.00 

.44 
.10 

.23 
.05 

100 
21.85 

Third  portion  (material  heated  3  hours 

P.ct. 

51.40 

14.92 

33.28 

.40 

100 

more). 

Vol. 

1.72 

.50 

1.12 

.01 

3.35 

110.  Basaltic  lava,  Kilauea,  Hawaii,  Cascade 

P.ct. 

88 

70.42 

21.41 

2.49 

2.01 

2.79 

100 

of  1868.    A  rather  porous  lava,  having  a 
specific  gravity  of  only  2.00. 
111.  Fresh  lava,  Vesuvius,  from  the  lava  stream 

Vol. 
P.ct. 

s          i 
8 

.  ' 
86 

.60 
73.22 

.18 
12.24 

.02 
2.33 

.02 

1.47 

.02 
1.88 

.85 
100 

of  April,  1906,  collected  by  F.  B.  Taylor, 

Vol. 

03 

.31 

.05 

.01 

.01 

.01 

.42 

March  30,  1907.    From  south  side  of  a 

quarry  in  front  of  the  church  in  Bosco 

Trecase,  above  Torre  Annunziata.    This 

specimen  came  from  10  ft.  below  the  top 
and  21  ft.  from  the  bottom  of  the  flow, 
which  had  been  blasted  at  this  point. 
7  112.  Fresh  lava,  Vesuvius,  same  flow  as  last; 

P.ct. 

23 

43 

63.49 

7.94 

2.33 

1.50 

1.31 

100 

0.5  kilometer  SE.  of  church  where  No. 

Vol. 

14 

.39 

.05 

.02 

.01 

.01 

.62 

Ill  was  collected.    About  8  ft.  below 

surface  and  2  ft.  from  bottom  of  bed. 

Collected  March  30,  1907,  by  F.  Taylor. 

1  No.  107.    Chemical  analysis  by  J.  M.  Davison  ;  Fe,  14.68;  Ni,  1.60;  Co,  .08;  8,1.37;  P,  .15;  SiO2,  35.82;  FeO, 
15.53;  MgO,  22.74;  CaO,  2.99;  A12O3,  3.60;  NaoO,  2.07;  K2O,  .32;  100.95. 

2  No.  108.    Average  of  13  analyses  compiled  by  Farrington  (  Pub.  Field  Columbian  Museum  No.  120,  pp.  82-84)  : 
Fe,  89.66;  Ni.7.90;  Co,  0.63;  P,  0.24;  S.0.14;  Si,  0.02;  Misc.,  0.57;  99.16. 

were  used,  but  with  these  there  was  included  a  little  rust,  which  adhered  to  the  metal 


magnet, 


3  Iron  borings  and  filings  w 
hen  it  was  withdrawn  with  a 

«The  material  used  in  this  determination  consisted  of  bright  borings  carefully  freed  from  rust,  a  pocket  of  which 
unfortunately  was  encountered  in  drilling.  But  in  spite  of  much  care  exercised  in  drawing  put  the  metallic  borings 
with  a  magnet,  some  rust  adhered  to  them  and  consequently  was  heated  with  the  metal  in  the  combustion  tube. 
However,  this  amounted  to  much  less  than  in  the  first  determination.  No  filings  were  used. 

6  For  this  determination  borings  from  the  interior  of  the  specimen  were  carefully  made  by  Wm.  Gaertner  &  Co., 
scientific-instrument  makers.    There  was  no  visible  rust  adhering  to  these  borings,  which  were  then  worked  twice, 
with  a  magnet,  without  any  impurities  being  left  behind.   The  white  paper  on  which  this  operation  was  performed 
failed  to  show  the  slightest  discoloration,  such  as  it  had  done  in  the  two  previous  determinations.    As  usual  the 
material  was  heated  at  100°  for  3  hours,  in  the  presence  of  P2O6,  and  then  allowed  to  stand  in  the  vacuum  overnight 
to  remove  all  free  moisture.    Though  the  vacuum  was  perfect  at  the  end  of  this  time,  the  first  two  pumpings  of  gas 
(amounting  to  0.2  cubic  centimeter)  which  were  evolved  when  heat  was  applied,  were  not  kept,  since  it  was  desired 
to  eliminate  atmospheric  air  as  a  source  of  nitrogen. 

A  comparison  of  the  three  determinations,  No.  108  shows  what  a  tremendous  effect  the  presence  of  a  little  iron 
rust  will  have  upon  the  gases  evolved  from  a  metallic  meteorite.  Much  of  this  gas  is  doubtless  derived  from  iron 
carbonate  and  the  hydrated  oxide  of  iron,  as  will  be  explained  under  the  topic  of  gas  due  to  chemical  reactions. 
Great  care  is  therefore  necessary  in  making  gas  analysis  of  iron  meteorites  to  avoid  any  contamination  of  rust. 

s  The  most  striking  feature  of  these  analyses  is  the  unusual  amount  of  sulphur  dioxide,  which  indicates  an 
oxidized  condition  of  the  ore. 

7  The  odor  of  sulphur  dioxide  was  very  prominent  in  the  gas  obtained  from  these  two  Vesuvian  lavas. 


THE   ANALYSES. 


GROUPINGS  AND  CLASSIFICATIONS  OF  ANALYSES. 

As  the  volumes  and  relative  proportions  of  the  gases  found  in  the  fore- 
going analyses  vary  within  wide  limits,  the  nature  of  this  variation  can 
best  be  shown  by  grouping  the  results.  To  make  these  tables  as  complete 
as  possible,  not  only  the  results  of  the  present  studies,  but  all  the  available 
analyses  of  other  investigators,  have  been  included  in  the  lists.  Except 
in  the  case  of  four  of  the  five  analyses  by  Tilden,  relative  to  which  suffi- 
cient data  are  not  given,  all  of  the  figures  in  these  tables  refer  to  volumes 
of  gas  per  volume  of  rock.  Previous  investigators  have  usually  given  the 
total  volume  of  gas  and  the  percentages  of  each  constituent.  From  these 
I  have  calculated  the  volumes  for  each  individual  gas. 

TABLE  9. — Analyses  classified  by  groups  of  rocks. 


No. 

Bock  and  locality. 

H2S. 

C02. 

CO. 

CH4. 

H2. 

N2. 

Total. 

Analyst. 

1 

2 
4 
9 
19 
20 
21 
22 
24 
25 
26 
33 
37 
38 
39 
57 
66 

44 
51 
53 
56 

15 
16 
17 
32 
36 
52 
58 
60 
73 
74 

11 

34 

Granites  and  gneisses  of  igneous  origin. 
Granite  Skye  (p  ct  )  . 

28.60 
.86 
4.50 
.28 
.42 
.31 
.37 
3.51 
1.89 
6.63 
1.89 
.16 
.39 
1.79 
.85 
1.13 
.08 
1.20 
carb. 
.28 

6.45 
.35 
.32 
.07 
.09 
.08 
.05 
.72 
.23 
1.13 
.13 
.05 
.09 
.18 
.15 
.11 
.03 
.05 
.27 
.13 

3.02 
.12 
.19 
.07 
.10 
.06 
.02 
.06 
.02 
.06 
.03 
.02 
.06 

".07 
.03 
.01 
.01 
.02 
.03 

61.68 
5.29 
2.36 
.92 
2.94 
1.50 
.04 
2.34 
.43 
1.37 
.74 
.38 
1.04 
.99 
1.79 
1.06 
.60 
.05 
.85 
.95 

5.13 
.04 
.16 
.10 
.11 
.13 
.12 
.22 
.23 
.08 
.15 
.04 
.02 

".12 

.05 
.04 
.05 
.04 
.08 

99.88 
6.71 
7.53 
1.44 
3.66 
2.08 
.60 
6.85 
2.80 
9.27 
2.94 
.65 
1.60 
2.96 
2.98 
2.38 
.76 
1.36 
1.22 
1.47 
3.19 

Tilden. 
Gautier. 
Do 
Chamberlin. 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 

Chamberlin. 
Do 
Do 
Do 

Tilden. 
Travers. 
Chamberlin. 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 

Tilden. 
Gautier. 
Do 
Chamberlin. 
Do 

Granite  Vire  (average) 

0.05 

Granitoid  porphyry,  L'Esterel  

Medium-grained,  white  granite  

Laurentian  gneiss,  Ontario  
Pike's  Peak  granite  

Fine-grained  gneiss,  Menominee  

tr 

Fine-grained  banded  gneiss,  Menominee. 
Laurentian  granite  Marquette 

Pink  granite,  North  Carolina  

tr 
tr 
tr 
tr 
tr 
tr 
tr. 
.04 
tr. 
tr. 

Gray  granite,  Quincy  ,  Mass  

Laurentian  gneiss,  Marquette  

Oglesby  blue  granite,  Georgia  
Stone  Mountain  granite  Georgia. 

Ortonville  granite.  Minn  

Granite  porphyry  bowlder,  New  York  — 
Gneiss  of  igneous  origin,  Ontario  

1.47 

.22 

.05 

1.36 

.09 

0.05 
.05 
.03 
.03 
.04 

1.90 

'.14 
.12 
.33 
.32 
.05 
.03 
.03 
.06 
.05 
.14 
.11 

.13 

.02 
tr. 
.25 
.57 

The  syenite  group. 
Nephelite  syenite,  Ontario  

0.29 
.11 
carb. 
.15 

0.05 
.06 
.11 
.07 

.07 

2.16 
.00 
.10 
.12 
.12 
.58 
.07 
.17 
.07 
.06 
.07 
.04 

0.04 
.05 
.08 
.03 
.05 

2.03 

".64 

.02 
.07 
.20 
.04 
.04 
.04 
.05 
.04 
.20 

0.25 
.95 
.22 
2.22 
.91 

88.42 
1.40 
1.13 
.97 
2.68 
8.54 
.52 
.93 
.45 
1.10 
1.29 
3.95 

2.09 

2.89 
4.52 
1.15 
3.83 
10.10 

0.68 
1.22 
.44 
2.50 
1.25 

100.01 
1.40 
1.81 
1.23 
3.64 
29.73 
.84 
2.25 
.87 
1.52 
1.78 
4.61 

Shonkinite,  Highwood  Mountains,  Mont. 

tr. 

Hornblende  syenite,  Maine  

tr. 

Average  of  4  analyses  

The  gabbro-diorite  group. 
Gabbro,  Lizard  England  (p  ct  )  

tr. 

.18 

5.50 
.00 
.40 
carb. 
.44 
20.07 
.16 
1.08 
.28 
.22 
.27 
.21 

Gabbro-diorite,  Mt.  Sneffels,  Colo  
Gabbro,  summit  of  Mt.  Sneffels  
Orthoclase  gabbro  Duluth 

.02 
tr. 
tr. 

".03 
.06 
.07 

Olivine  gabbro  Duluth        

Theralite,  Crazy  Mountains,  Mont  
Intrusive,  Highwood  Mountains,  Mont.  . 
Diorite  plug  in  shales,  Colorado  
Coarse  diorite  bowlder  Maine 

Diorite,  Penobscot  Bay,  Me  
Average  of  11  analyses  

.02 

2.31 

2.57 
2.39 
12.29 
.59 
20.08 

.13 

1.61 
.33 
.31 
.05 
1.16 

.07 

0.80 
.08 
tr. 
.19 
.09 

4.73 

8.00 
7.58 
15.61 
4.91 
32.19 

JXabases  and  basalts. 
Basalt  Antrim 

Ophite,  Villefranque  (average)  
Lherzolite,  Lherz  

.24 
1.86 

Keewatin  greenstone,  Mesabi  

.19 

24 


THE    GASES   IN    ROCKS. 
TABLE  9. — Analyses  classified  by  groups  of  rocks. — Continued. 


No. 

Bock  and  locality. 

HsS. 

C02. 

00. 

CH* 

H2. 

K|. 

Total. 

Analyst. 

35 

45 
50 
61 
84 
85 
110 
111 
112 

13 
47 
62 
64 
70 
72 
91 

10 
49 

59 

3 
23 

14 

78 

71 
83 
100 
103 
105 

27 
28 
29 
30 
31 
43 
54 
55 

65 

67 

69 
92 

Diabases  and  basalt*—  Cont. 

0.01 
tr. 
.05 
.19 

tr. 
.01 
.03 
.14 

0.25 
3.74 
1.07 
4.91 
carb. 
1.31 
.60 
.31 
.39 

0.06 
1.74 
.20 
.21 
.14 
.09 
.18 
.05 
.05 
.44 

.09 
.57 
.27 
.04 
.16 
.05 
.05 

0.06 
.17 
.06 
.12 
.03 
.09 
.02 
.01 
.02 

3.15 
2.24 
1.16 
3.13 
1.08 
2.34 
.02 
.01 
.01 
2.54 

.08 
.12 
.30 
.17 
.53 
.19 
.01 

0.06 
.16 
.10 
.15 
.05 
.05 
.02 
.01 
.01 

3.59 
8.05 
2.64 
8.71 
1.30 
3.88 
.85 
.42 
.62 

Chamberlin. 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 

Chamberlin. 
Do 
Do 
Do 
Do 
Do 
Do 

Chamberlin. 
Do 

Do 
Do 

Chamberlin. 
Do 

Chamberlin. 
Do 

Wright. 
Chamberlin. 
Do 
Do 
Do 
Do 

Tilden. 
Do 
Chamberlin. 
Do 
Do 
Do 
Do 
Do 
Do 
Do 

Do 

Do 
Do 
Do 
Do 

Iron  basalt,  Greenland  
Nephelite  melilite  basalt,  Texas  
Diabase  Nahant  Mass 

Keweenawan  diabase,  Michigan  
Basalt  of  1868.  Kilauea,  Hawaii  
Lava  of  1906  Vesuvius 

Lava  of  1906,  Vesuvius  

.19 

3.% 

carb. 

5.12 
carb. 
.56 
2.66 
.76 
.22 

.12 

.02 

.30 
.05 
.01 
.03 
.03 
.00 
.06 

.04 
.03 

V  ^ 

.1 

.11 

.08 
.26 
.13 
.02 
.05 
.06 
.03 
.09 

.13 
.03 

.03 

7.36 

.27 
6.37 
.75 
.80 
3.43 
1.08 
.31 

AndesUes. 
Andesite  Ouray  Co.  Colo  

Andesite,  Red  Mountain,  Ariz  
Andesite  Rosita  Hills  Colo 

tr 
tr 
tr 
tr 
tr 

Andesite'  Granite  Mountain,  Utah  
Phono!  ite  trachyte,  Pike's  Peak  
Andesite,  summit  of  Orizaba  

Average  of  7  analyses  

^ 

1.86 

.22 
2.33 

.07 
.15 

.18 

.08 
.05 

.06 
.05 

.28 
.10 
.19 

.05 
.08 
.06 

.00 
.09 
tr. 
.03 
.02 
.05 

.20 

.03 

.07 

3 

2.39 

.50 
2.51 

.20 
.27 
.87 

12.03 
3.72 

7.87 

.30 

.97 
.79 

.07 
.81 
.08 
.88 
.13 
.20 

Ehyolites. 
Rhyolite  Marble  Mountain  Arizona 

Rhyolite  vitrophyre  Telluride 

Pitchstone  rhyolite,  Rosita  Hills  

Nevadite,  Chalk  Mountain,  Colo  

.01 
.02 

.05 
.04 

.05 

.02 
.05 
.04 

.00 
.03 
tr. 
.04 
tr. 
.00 
.01 

0.56 
51 
14 
11 
02 
08 
01 

.03 
.04 
.02 

.02 
.06 

3.81 
3.07 

^ 

.69 

7.67 
.46 

.05 

.22 

.05 

Schists. 
Keewatin  schist,  Mesabi  
Schist  with  chloritoid,  Black  Hills  

Average  

i= 

4.06 

carb. 
.32 

3.44 

.22 
.44 

.13 

.01 
.08 
.04 

tr. 
.05 
.03 
.02 
.01 
.03 
.02 

1.16 
0.56 
.04 
.10 
.04 
.08 
.03 
.07 
.04 
.02 

.06 

.06 
.06 
.13 

.05 

Miscellaneous  porphyries. 
Coarse  porphyry,  Ouray  Co.,  Colo  
Topaz  quartz-porphyry,  Saxony  

tr. 

'tr.' 
.01 

"tr." 

.32 

.07 
.11 
.03 
.66 
.09 
.12 

.33 

.00 
.53 
.01 
.12 
.01 
tr. 
.11 

12.49 
61.93 
4.32 
4.02 
.65 
1.90 
.37 
.05 
.45 
.41 

Quartz. 
Smoky  quartz,  Branchville,  Conn  
Vein  quartz,  Iron  Co.,  Utah  
Crystals  (aqueous  origin)  ,  North  Carolina. 
Auriferous  quartz,  New  South  Wales  .  .  . 
Quartz  from  pegmatite,  Baltimore  
Quartz  from  lava,  Utah  

.18 

77.72 
31.62 
.13 
1.35 
.19 
.19 
.26 

J2.05 
carb. 
.16 

}.ee 

carb. 
carb. 

.47 
2.23 

.03 

8.06 
5.36 
.10 
.22 
.07 
.08 
.09 
.09 
.15 
.07 

.48 
.26 
.16 
1.10 

.35 

99.99 
99.98 
4.73 
6.10 
.97 
2.33 
.76 
5.05 
.68 
.79 

4.88 

.90 
2.31 
3.22 
6.40 
3.18 

Metamorphosed  sedimentaries. 
Pyroxene  gneiss,  Ceylon  (p.  ct.  )  
Gneiss,  Seringapatam  (p.  ct.)  

Baltimore  gneiss,  Bryn  Mawr,  Pa  
Baltimore  gneiss,  Schuylkill  River  
Wissahickon  mica  gneiss,  Pennsylvania  . 
Wissahickon  gneiss,  Schuylkill  River  
Cambrian  gneiss,  Coatesville,  Pa  
Sillimanite  gneiss,  Quebec  { 
Altered  Jurassic  shale  Colorado 

tr. 
.30 
tr. 
tr. 

sbj 

2.76 
tr. 
.11 

4s?! 

tr. 
tr. 
16 

Fine-grained  gneiss,  Ontario  j 

.( 
,  ' 
.03 
.05 
.05 
.10 

5 

I  , 

.32 

2.01 
2.32 
2.84 

Amphibolite,  Ontario  

Rice  Rock,  Sudbury,  Ontario    
Amphibolite,  Chester,  Mass  

Average  of  13  analyses  

.57 

.77 

.22 

.05 

1.52 

THE    ANALYSES. 
TABLE  9. — Analyses  classified  by  groups  of  rocks. — Concluded. 


25 


No. 

Bock  and  locality. 

HsS. 

C02. 

CO. 

CHj. 

H2. 

N,. 

Total. 

Analyst. 

5 

6 

Shales* 
Kinderhook  shale,  Burlington,  Iowa  
Portage  shale  Ithaca  N  Y 

9.28 
1  47 

0.35 
83 

0.12 
16 

0.22 
1  23 

0.15 
leak 

10.12 

Chamb6rlin. 

18 

tr 

41 

17 

07 

1  45 

41 

Hamilton  shale,  Nashville,  Tenn  

29.38 

20.10 

4.38 

3703 

9089 

Do 

42 

Oil  shale,  Platteville,  Wis  

3.90 

10.43 

4.82 

20.67 

7.57 

1.26 

48.65 

Do 

8 

Average  of  first  3  analyses  

Sandstones  and  quartzites. 
Potsdam  sandstone,  Baraboo,  Wis  

== 

3.75 
.47 

.45 
.18 

.11 

.97 
01 

.18 
38 

5.43 
1  04 

12 

Quartzite  schist,  Baraboo,  Wis. 

16 

07 

03 

03 

06 

35 

Do 

75 
76 

77 
78 

Potsdam  sandstone,  Ablemans,  Wis  
Same  as  last,  powdered  and  reheated  — 
Huronian  quartzite,  Baraboo,  Wis  
Red  Beds  Colorado  City 

tr. 
tr. 
tr. 
tr 

.09 
.05 
.11 

.05 
.07 
.04 
71 

.02 
.02 
.01 
07 

.13 
.23 
.24 
32 

.05 
.08 
.03 

06 

.34 
.45 
.43 
1  16 

Do 
Do 
Do 
Do 

80 
81 
82 
97 
98 
99 

St.  Peter  sandstone,  Minnehaha  Falls  
Same  as  last,  powdered  and  reheated  — 
Quartzite,  Grenville  series,  Quebec  
Micaceous  quartzite,  Uinta  Mountains.  .  . 
Quartzite,  Rib  Hill,  Wis  
Same  as  last,  granules  used  

tr. 

'.'23 
.01 
.01 
tr. 

.02 
.03 
.21 
.57 
.62 
.86 

tr. 
.07 
.04 
.12 
.06 
.01 

.01 
.01 
.01 
.03 
.02 
tr. 

tr. 
.17 
.09 
.63 
.17 
.02 

.01 
.21 
.01 
.06 
.02 
tr. 

.04 
.49 
.59 
1.42 
.90 
.89 

Do 
Do 
Do 
Do 
Do 
Do 

Averasre  of  12  analvses  

.02 

.29 

.11 

.02 

.17 

.08 

.69 

i  The  two  bituminous  shales  which  derived  the  bulk  of  their  gas  from  the  distillation  and  decomposi- 
tion of  organic  matter  are  necessarily  omitted  from  the  average. 


TABLE  10. — Various  minerals. 


NO. 

Mineral  and  locality. 

BLS. 

CO* 

CO. 

H2. 

CH*. 

N2. 

A  + 
He. 

Total. 

Analyst. 

Feldspar  . 

120 

001 

003 

001 

002 

127 

Celestial  graphite 

6  66 

18 

39 

tr 

7  25 

Do 

Graphite,  Borrodale  
Chlorite,  Zoptan,  Moravia  

.95 
.33 

.20 
1.33 

.58 
5.84 
208 

.68 

.17 

2.60 
7.50 
208 

Do 

Travers. 
Do 

Mica,  Westchester,  Pa  
Talc,  Greiner,  Tyrol  

.42 
.19 
3  08 

^     -        -.» 

.2 
.1 

E 

' 
2 
1 
5 

.64 
.30 
363 

Do 
Do 
Do 

7 

Malacone  

1.55 
126 

.12 

.03 
10 

04 

.02 
.27 

.17 

1.77 
179 

Kitchin  and 
Winterson. 
Chamberlin 

40 
48 
63 
90 
93 
94 
95 
96 
101 
102 
104 

Biotite,  Ortonville  granite  
Pyroxene  crystals,  Red  Mountain 
Anorthosite,  Quebec  
Wollastonite,  Lewis  Co.,  N.  Y.  .  .  . 
Pitchblende,  Beaver  Co.,  Colo  
Carnotite  
Greenalite  rock,  Mesabi  
Griinerite  rock,  Mesabi  
Beryl,  pegmatite,  New  England  .  . 
Pegmatite  with  tourmaline  
Albite,YanceyCo.,N.  C  

0.22 
.10 
tr. 

su'l'. 
tr. 
tr. 
.02 
tr. 
tr. 

12.45 
.69 
2.36 
2.37 
carb. 
2.46 
.42 
1.14 
.16 
.06 
tr. 

.23 
.16 
.27 
.18 
.24 
.23 
.24 
.26 
.01 
.06 
.01 

.30 
.08 
.56 
.06 
.07 
.05 
5.18 
1.39 
.31 
1.45 
.04 

.06 
.01 
.02 
.02 
.03 
.02 
tr. 
.02 
.01 
.05 
.02 

.21 
.06 
.06 
.08 
.27 
.22 
.15 
.19 
.02 
.04 

'.37' 
.04 

13.47 
1.10 
3.27 
2.71 
.98 
3.02 
5.99 
3.02 
.50 
1.66 
.07 

Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 
Do 

Average  of  21  analyses  

.02 

1.88 

.19 

.92 

.06 

.08 

.03 

3.18 

It  should,  perhaps,  be  stated  that  in  making  this  and  other  averages 
of  analyses,  in  those  cases  where,  on  account  of  excessive  carbonation,  no 
figures  are  given  for  carbon  dioxide,  the  average  amount  of  this  gas  cal- 
culated from  the  other  analyses  is  assumed  to  be  present  in  those  rocks 
marked  "carbonated."  This  addition  is  added  to  the  average  total  and 
makes  this  figure  slightly  greater  than  the  average  of  the  column  which  it 
foots.  The  same  method  has  been  used  for  carbon  monoxide  in  the  three  of 
Travers's  analyses  where  carbon  monoxide  and  hydrogen  are  put  together. 


26 


THE    GASES   IN    ROCKS. 


TABLE  11. — Stony  meteorites. 


No. 

Meteorite. 

H2S. 

C02. 

CO. 

CH4- 

H, 

N2. 

Total. 

Analyst. 

180 

013 

006 

0.95 

005 

299 

Wright 

Pultusk  Poland  

1.06 

.06 

.06 

.52 

.04 

1.75 

Do 

2.13 

.04 

.05 

.36 

.04 

263 

Do 

283 

08 

04 

46 

08 

349 

Do 

.88 

.05 

1.45 

.12 

2.50 

Do 

Kold  Bokkeveld  

23.49 
1  59 

.61 
03 

.82 
.10 

.10 
73 

.21 
03 

25.23 
251 

Do 

Dewar 

Pultusk  Poland  

2.34 

.19 

.27 

.64 

.09 

3.54 

Do 

Mocs                                     

1.25 

.07 

.09 

.45 

.07 

1.94 

Do 

r 

Orgueil                                                     ] 

S02 

1-740 

1.H 

87 

33 

5787 

Do 

106 

Allegan  Mich  

48.03 
tr. 

1    7! 

.19 

.01 

.08 

tr. 

.49 

Chamberlin. 

107 

Estacado,  Texas  

tr. 

.24 

.25 

.03 

.81 

.01 

.84 

Do 

400 

377 

24 

20 

50 

09 

8  80 

The  figures  for  the  Orgueil  meteorite  which  yielded  such  a  remarkable 
amount  of  sulphur  dioxide  make  the  average  for  the  sulphur  gases  an  abnor- 
mal one.  The  presence  of  this  gas  in  quantity  must  mean  that  the  meteor- 
ite has  suffered  much  from  weathering  and  oxidation  subsequent  to  its 
fall.  Considerable  troilite  has  passed  into  iron  sulphate  which  has  been 
decomposed  by  the  heat  of  the  combustion-furnace. 

Omitting  the  sulphur  dioxide  of  this  specimen,  the  average  total  volume 
of  gas  from  stony  meteorites  is  reduced  to  4.80  times  the  volume  of  the 
meteoritic  material. 

TABLE  12. — Iron  meteorites. 


No. 

Meteorite. 

HjS. 

C02. 

CO. 

CH4. 

H2. 

N2. 

Total. 

Analyst. 

0.13 

000 

2.44 

028 

285 

31 

121 

1  14 

51 

3  17 

Mallet 

Tazewell  Co.,  Tenn  

.46 

1.31 

1.35 

.05 

3.17 

Wright. 

Shingle  Springs,  Cal  

.13 
11 

.12 
19 

.67 
99 

.05 

.97 
1  29 

Do 
Do 

29 

34 

1  57 

2  20 

Do 

Arva,  Hungary  

5.92 

31.91 

8.57 

.73 

47.13 

Do 

04 

1.13 

016 

163 

63 

359 

Flight  i 

33 

47 

4  % 

62 

6  38 

Do 

108 

Toluca,  Mexico  

tr. 

.12 

1.32 

04 

.27 

.10 

1.85 

Chamberlin. 

78 

3  80 

02 

2  36 

30 

7  26 

Average  omitting  Arva  meteorite. 

.21 

.67 

.02 

1.67 

.24 

2.83 

i  Flight,  Phil.  Trans.  No.  172  (1882),  pp.  893-894  and  p.  896. 

Methane  was  determined  in  only  two  of  these  analyses.  In  these  two 
it  averaged  0.10  volume;  but  in  order  to  make  the  figures  consistent  in  the 
table,  it  was  necessary  to  average  these  as  if  the  eight  other  meteorites 
yielded  no  marsh-gas,  though  it  is  highly  probable  that  this  gas  was  present 
and  has  been  included  in  the  figures  given  for  hydrogen. 

The  unusual  amount  of  gas  from  the  Arva  specimen  recalls  the  be- 
havior of  the  Toluca  meteorite,1  which,  at  the  first  attempt,  produced  24.42 
volumes  of  gas,  owing  to  the  presence  of  a  small  quantity  of  iron  rust,  but 
whose  pure  metal  evolved  only  1.85  volumes.  An  average,  omitting  the 
Arva,  is  therefore  made. 


Ante,  p.  22. 


THE    ANALYSES. 


27 


AVERAGES    OP   THE    GROUPS. 
TABLE  13. — Igneous  rocks. 


Order. 

Type  of  rock. 

No.  of 
analy- 
ses. 

HaS. 

C02. 

CO. 

CH4. 

Ha. 

•» 

Total. 

1 

Basic  schists  

2 

0.00 

4.06 

0.19 

0.05 

3.44 

013 

7  87 

2 
3 

4 

Diabases  and  basalts  
Gabbros  and  diorites  

14 
11 
19 

.19 
.02 
.00 

3.96 
2.31 
147 

.44 
.13 

22 

.12 
.07 
05 

2.54 
2.09 
1  36 

.11 
.11 
09 

7.36 
4.73 
3  19 

5 

Andesites  

7 

.00 

1.86 

.18 

.06 

.20 

.09 

2  39 

6 

7 

Syenites  
Rhyolites 

4 
4 

.00 
00 

.18 

.07 
05 

.05' 
02 

.91 
06 

.04 
05 

1.25 

87 

g 

2 

00 

32 

06 

04 

33 

04 

79 

The  general  averages  bring  out  the  fact  that,  while  rocks  of  each  group 
may  vary  considerably  among  themselves,  each  group  as  a  whole  fits  into 
a  logical  place  in  relation  to  the  other  groups.  The  established  order 
appears  to  be,  most  gas  from  those  rocks  which  contain  the  greatest  pro- 
portion of  ferromagnesian  minerals.  Though  much  influenced  by  other 
conditions,  such  as  relative  age  and  nature  of  the  igneous  mass,  the  general 
deduction  may  be  made  that  the  volume  of  gas  obtained  from  rocks 
varies,  in  a  rough  way,  in  proportion  to  the  percentage  of  ferromagnesian 
minerals  present.  Diabases,  basalts,  and  basic  schists  take  first  rank  in 
the  quantity  of  gas  evolved.  Next  to  them  appear  diorites  and  gabbros 
which  are  also  near  the  basic  end,  but  formed  under  different  conditions. 
Andesites  are  out  of  their  place  in  this  list,  as  they  take  precedence  over 
granites  in  the  proportion  of  ferromagnesian  minerals,  but  these  andesites 
were  all  either  of  Tertiary  or  Recent  age,  whereas  most  of  the  granites  came 
from  Pre-Cambrian  formations,  and,  as  the  next  table  will  show,  ancient 
igneous  rocks  yield  more  gas  than  modern  ones.  The  rhyolites,  which  com- 
bine a  scarcity  of  basic  minerals  with  Tertiary  age,  foot  the  list. 

It  is  to  be  noted  that  the  rank  of  a  type  of  rock  on  the  basis  of  an 
individual  gas  does  not  in  all  cases  correspond  to  its  rank  for  some  other 
gas,  or  in  respect  to  total  volumes.  The  andesites  tested  gave  more  carbon 
dioxide  than  either  the  granites  or  the  syenites,  though  both  of  these  types 
greatly  surpassed  the  andesites  in  the  matter  of  hydrogen.  But  this  in- 
volves another  factor:  in  deep-seated  rocks,  hydrogen  and  carbon  dioxide 
are  of  about  equal  importance;  in  surface  flows,  carbon  dioxide  predomi- 
nates. Though  carbon  monoxide  and  methane  are  somewhat  variable, 
the  minor  gases  generally  increase  or  decrease  with  the  total  volumes. 

TABLE  14. — Rocks  of  sedimentary  origin. 


No.  of 

Sul- 

Order. 

Type  of  rock. 

analy- 

phur 

C02. 

CO. 

CH4. 

H2. 

N2. 

Total. 

ses. 

gases. 

1 

Shales  (non-bituminous)  

3 

0.00 

3.72 

0.45 

0.11 

0.97 

0.18 

5.43 

2 
3 

Metamorphosed  sediments  
Sandstones  and  quartzites  

13 
12 

.57 
.02 

.77 
.29 

.22 
.11 

.05 
.02 

1.52 
.17 

.05 
.08 

3.18 
.69 

Among  sedimentary  rocks,  sandstones  and  quartzites  yield  less  gas 
than  shales,  while  the  metamorphic  group,  comprising  both  altered  shales 
and  sandstones,  together  with  modified  limestones,  take  an  intermediate 
position,  though  they  surpass  shales  in  hydrogen  and  the  sulphur  gases. 


28 


THE    GASES   IN    ROCKS. 


TABLE  15.— Meteorites. 


No.  of 

Sul- 

Order. 

Type  of  meteorite. 

analy- 

phur 

COo. 

CO. 

CH4. 

H2. 

N5. 

Total. 

ses. 

gases. 

1 

Stony 

12 

4  00 

3  77 

0  24 

0  20 

0  50 

0  09 

8  80 

2 

Without  S02  of  Orgueil  
Iron  

12 
10 

.00 
.00 

3.77 

.78 

.24 
3.80 

.20 
.02 

.50 

2.36 

.09 
.30 

4.80 
7.26 

9 

00 

21 

67 

02 

1  67 

24 

2  83 

A  comparison  of  the  two  types  of  meteorites  indicates  that  carbon 
dioxide  is  much  more  important  in  the  gas  from  stony  specimens  than  in 
that  from  the  metallic  bodies,  but  that  iron  meteorites  yield  several  times 
as  much  carbon  monoxide  and  hydrogen  as  do  the  stones.  Sufficient  data 
are  not  at  hand  to  permit  a  comparison  of  the  amount  of  marsh-gas  from 
these  two  types;  nitrogen,  however,  appears  to  come  in  greater  volume  from 
the  iron  meteorites. 

ANALYSES    CLASSIFIED    BY   THE   AGE    OP   THE    ROCKS.1 
TABLE  16. — Igneous  rocks. 


Order. 

Age. 

No.  of 
analy- 
ses. 

H2S. 

C02. 

CO. 

CH4. 

H2. 

N2. 

Total. 

2 

Archean  

7 
8 

0.03 
.00 

7.44 
1  85 

0.35 
31 

0.07 
07 

3.79 
208 

0.21 
16 

11.89 
4  47 

3 

Tertiary 

18 

00 

1  20 

13 

05 

53 

07 

1  98 

4 

Recent  lavas  

5 

.03 

.41 

.07 

.01 

06 

.02 

60 

Total  Pre-Cambrian  
Grand  total  

28 
51 

.02 
.01 

2.76 
2.16 

.23 
.18 

.06 
.05 

2.12 
1.36 

.12 
.09 

5.31 
385 

In  addition  to  those  rocks  which  could  be  classed  either  as  Archean  or 
Proterozoic,  there  were  others  which  could  only  be  called  Pre-Cambrian; 
they  are  included  under  the  head  of  Total  Pre-Cambrian. 

The  rapid  and  steady  decline  in  the  quantity  of  every  gas,  in  passing 
down  the  columns  from  the  Archean  through  the  Proterozoic  and  Tertiary 
to  Recent  lavas,  is  very  striking.  These  differences  may  be  due  to  a  com- 
bination of  causes.  The  older  rocks  may  yield  more  gas  than  the  recent, 
owing  to  metasomatic  changes  which  have  been  slowly  taking  place  within 
the  rocks.  If  this  be  so,  the  analyses  indicate  that  this  process  is  progress- 
ing at  an  exceedingly  slow  rate.  Or  the  early  magmas  may  have  been  more 
highly  charged  with  gas,  some  of  which  has  escaped  as  they  were  worked 
over  and  over  and  brought  to  the  surface  in  later  times.  Both  of  these 
processes  have  probably  been  operative. 

TABLE  17. — Sedimentary  and  meta-sedimentary  rocks. 


Order. 

Age  of  rocks. 

No.  of 
analy- 
ses. 

at 

C02. 

CO. 

CH4. 

H2. 

N2. 

Total. 

I 

17 

045 

068 

017 

0  04 

1  32 

0  05 

2  71 

2 

10 

.00 

1.34 

.25 

.05 

.41 

.13 

2.28 

3 

1 

.00 

carb. 

.15 

.04 

.45 

04 

68 

Total  

28 

.27 

93 

.20 

.04 

.96 

.08 

2.48 

1  In  this  classification  of  analyses  by  the  age  of  the  rocks,  and  in  the  following  one 
based  on  granularity,  only  my  own  analyses  have  been  used. 


THE    ANALYSES. 


29 


Age  appears  to  make  less  difference  in  the  gas  evolved  from  sedimentary 
or  meta-sedimentary  rocks  than  it  does  in  the  case  of  igneous  rocks.  All 
of  the  Proterozoic  specimens  were  of  metamorphic  types,  while  only  one 
of  the  Paleozoic  sediments  had  been  metamorphosed.  The  Mesozoic  repre- 
sentative was  a  Jurassic  shale  altered  by  an  intrusive.  The  unusual  amount 
of  sulphur  gas  in  the  Proterozoic  list  is  due  to  two  weathered  rocks  which 
contained  iron  sulphate.  However,  even  with  these  omitted,  the  hydrogen 
sulphide  is  abnormally  high  in  the  rocks  of  this  age.  One  of  the  Paleozoic 
shales  was  so  calcareous  as  to  yield  9.28  volumes  of  carbon  dioxide,  which 
accounts  for  the  large  quantity  of  this  gas.  The  two  bituminous  shales 
(analyses  41  and  42)  are  not  included  in  these  averages,  since  their  exces- 
sive volume  of  gas  from  organic  sources  would  so  influence  the  figures  as 
to  disguise  some  of  the  characteristics  of  the  other  rocks. 

ANALYSES    CLASSIFIED    BY    THE    GRANULARITY    OF   THE   ROCKS. 
TABLE  18. — Igneous  rocks. 


Order. 

Granularity. 

No.  of 
analy- 
ses. 

HjS. 

C02. 

CO. 

CH4. 

H2. 

N2. 

Total. 

1 
2 

Fine-grained  
Medium-grained  

22 
18 

0.02 

.01 

2.75 

2.37 

0.31 
.17 

0.06 
.05 

1.68 
1.41 

0.12 
.10 

4.94 
4.11 

3 

4 

Coarse-grained  
Various  porphyries  (  mostly  Ter- 
tiary) 

11 
5 

.01 

oo 

.40 
41 

.10 
07 

.04 
04 

1.20 

22 

.08 
05 

1.83 
79 

From  this  table  it  would  appear  that  the  fine-grained  rocks  give  off 
more  gas  than  those  of  coarser  granularity.  One  of  the  reasons  for  this 
difference  probably  lies  in  the  fact  that  metasomatic  changes  are  favored 
in  fine-grained  rocks,  whose  crystals,  being  smaller,  afford  more  numerous 
junction-planes  between  the  crystals,  through  which  solutions  more  readily 
traverse  the  rock  than  in  the  coarse-grained  varieties.  Among  other 
changes,  hydration  and  carbonation  should  alter  fine-grained  rocks  more 
effectively  than  coarse-grained  ones. 

Fineness  of  grain  in  igneous  rocks  usually  means  that  the  lava  cooled 
rapidly,  and  this  would  hinder  the  escape  of  the  inclosed  gas.  But  in  the 
process  of  slow  crystallization,  such  as  produces  large  crystals  and  coarse 
texture,  much  more  of  the  gas  would  be  likely  to  be  crowded  out  of  the 
growing  crystals.  However,  as  a  general  rule,  fine-grained  igneous  rocks 
are  surface  flows,  while  coarse-texture  types  were  formed  at  some  depth 
below  the  surface,  and  hence  a  larger  proportion  of  whatever  gas  was 
expelled  from  the  rapidly  cooling  lavas  would  be  more  likely  to  escape 
altogether  than  would  be  the  case  with  the  gas  which  was  excluded  from 
growing  crystals  in  deeper  horizons,  as  in  bathylithic  intrusions,  where  final 
escape  was  difficult.  In  this  problem  of  granularity,  as  in  the  matter  of  age, 
the  quantities  of  gas  evolved  are  probably  determined  by  a  combination  of 
complex  factors  rather  than  by  any  single  cause. 

RESULTS  AT  DIFFERENT  TEMPERATURES. 

The  different  gases  are  not  all  expelled  from  rock  material  at  the  same 
temperature,  nor  are  they  evolved  at  the  same  rate.  In  general,  hydro- 
gen sulphide  and  carbon  dioxide  are  not  only  the  first  gases  to  appear,  but 


THE    GASES   IN    ROCKS. 


they  are  more  rapidly  given  off  than  the  others.  Carbon  monoxide  follows 
the  dioxide  as  the  temperature  is  raised,  and  generally  increases  in  relative 
importance,  as  the  latter  begins  to  subside,  toward  the  end  of  the  com- 
bustion. Hydrogen  and  marsh-gas  are  most  conspicuous  at  high  temper- 
atures, and  hence  attain  higher  percentages  in  the  last  half  of  the  gas  than 
in  the  first  portion.  Nitrogen  appears  to  be  disengaged  with  much  difficulty, 
requiring  considerable  time  at  an  elevated  temperature.  These  general 
facts  may  be  graphically  represented  by  plotting  the  curves  based  on  the 
experiments  with  the  Baltimore  gneiss.1  (See  fig.  1.) 


6.82 


<.S4 


.61 


100        200 


300        400         500        600 
Temperature 


700       800  850 


Fio.  1. — Plot  of  curves  representing  volume  of  each  gas  per  volume  of  rock 
obtained  at  different  temperatures  from  Baltimore  gneiss. 

Nitrogen  is  omitted  from  this  diagram  owing  to  an  unfortunate  leak- 
age of  air  during  a  part  of  the  experiment,  which  was  sufficient  to  vitiate 
the  results  for  this  gas. 

1  For  tables,  see  pp.  36-37. 


ABSORPTION.  31 

ABSORPTION. 

To  determine  how  much  gas  might  be  reabsorbed  after  being  expelled  by 
heat,  it  was  thought  desirable  to  use  a  rock  capable  of  producing  a  large 
volume  of  gas.  For  this  purpose  a  diabase  from  Nahant,  Massachusetts, 
which  yielded  13.9  volumes  of  gas,  was  selected.  This  material  was  heated 
at  full  blast  until  the  gas  evolution  had  practically  ceased,  which  required 
about  four  hours;  182  cubic  centimeters  of  gas  were  obtained.  After  allow- 
ing the  powder  to  remain  in  the  vacuum  overnight,  it  was  removed  and 
still  more  finely  pulverized  in  an  agate  mortar.  It  was  then  submitted  to 
forced  heat,  yielding  an  additional  20  cubic  centimeters  of  gas  in  six  hours. 
On  the  third  day  the  powder  gave  up  but  1  cubic  centimeter  in  four 
hours.  As  practically  all  the  gas  available  under  these  conditions  was  now 
removed,  the  heat  was  turned  off,  and  132.01  cubic  centimeters  of  this  gas 
(at  27.0°  and  758  millimeters)  immediately  introduced  into  the  combustion- 
tube,  which  was  allowed  to  cool.  At  the  end  of  43  hours  101.84  cubic 
centimeters  (at  20.0°  and  750  millimeters)  remained  to  be  pumped  out. 
This  being  equivalent  to  103.73  cubic  centimeters  at  27.0°  and  758  milli- 
meters, leaves  28.28  cubic  centimeters  as  the  volume  of  gas  absorbed  by 
the  powder.  The  material  in  the  tube  was  now  heated  for  2|  hours,  but 
only  3.47  cubic  centimeters  could  be  extracted  before  the  gas  evolution 
ceased.  Of  this,  carbon  dioxide  constituted  more  than  85  per  cent.  There 
still  remain  24.81  cubic  centimeters  lost  in  the  operation — a  loss  which  is 
probably  to  be  attributed  to  the  oxidation  of  that  quantity  of  hydrogen 
to  water  by  ferric  oxide,  while  the  tube  was  cooling.  This  water-vapor 
being  removed  by  the  calcium  chloride  drying-tube,  hydrogen  could  not 
be  again  freed  by  the  reverse  reaction  when  the  tube  was  reheated.  The 
carbon  dioxide  may  be  explained  by  carbonation  of  iron  or  calcium  and 
the  subsequent  decomposition  of  these  carbonates  when  heated  the  second 
time. 

In  order  to  ascertain  how  much  absorption  there  might  be  at  ordinary 
temperatures,  72  cubic  centimeters  of  the  remaining  gas,  from  which  the 
carbon  dioxide  had  been  removed,  since  carbonation  is  a  recognized  proc- 
ess, was  allowed  to  stand  in  the  tubes  for  eight  days.  At  the  end  of  this 
time  no  appreciable  quantity  of  the  gas  had  been  absorbed.  From  this 
and  the  preceding  experiment,  it  is  quite  evident  that  while  rock  material 
may  take  up  certain  gases  while  cooling  from  a  higher  temperature  under 
special  conditions,  at  ordinary  temperatures  absorption,  if  it  goes  on  at 
all,  takes  place  very  slowly.  Reversible  chemical  reactions  undoubtedly 
play  an  important  part  in  such  absorption  as  takes  place  under  changing 
temperatures. 

Professor  Dewar  experimented  with  celestial  graphite  to  ascertain  its 
absorbing  power  for  certain  gases.  After  exhausting  the  graphite  of  its 
gases,  dry  carbon  dioxide  was  drawn  through  the  tube  for  twelve  hours 
at  ordinary  temperatures.  The  tube  was  then  heated  and  about  1.1  vol- 
umes of  gas,  containing  98.4  per  cent  carbon  dioxide,  pumped  off.  The 
graphite  on  the  first  heating  had  given  7.25  volumes  of  gas,  of  which  91.8 
per  cent  was  carbon  dioxide.  Dry  marsh-gas  was  next  passed  over  the 


32 


THE    GASES   IN   ROCKS. 


powder  for  twelve  hours;  upon  heating,  only  0.9  volume,  containing  94.1 
per  cent  carbonic  acid,  was  obtained.  The  same  experiment  repeated  with 
hydrogen  gave  only  0.17  volume,  in  which  carbon  dioxide  reached  95  per 
cent.1  From  these  figures  it  would  seem  that  absorption  is  not  very  im- 
portant. The  steadily  decreasing  volumes  of  gas  with  each  successive 
heating  show  the  difficulty  with  which  the  gas  is  expelled,  for  apparently 
it  is  liberated  more  readily  after  an  interval  of  time  than  if  reheated  im- 
mediately. Hence,  unless  the  material  used  be  completely  deprived  of  its 
gas,  there  is  always  a  danger  in  assigning  to  absorption  what  may,  in  reality, 
be  only  the  last  portions  of  the  original  gas. 

Wright  used  another  method  in  testing  the  hypothesis  that  the  gas 
obtained  from  meteorites  has  been  derived  from  our  atmosphere  by  a 
process  of  absorption.  He  believed  that  if  the  gas  be  due  to  absorption 
from  the  earth's  atmosphere,  a  meteorite  should  have  stored  up  more  of 
it  after  being  exposed  for  a  considerable  period  than  shortly  after  its  fall. 
His  original  analysis  of  the  gas  from  a  meteorite  which  fell  in  Iowa  County, 
Iowa,  on  February  12,  1875,  was  made  a  short  time  after  its  fall.  A  year 
later,  to  extract  the  same  quantity  of  gas  from  another  fragment  of  the 
same  meteorite  required  not  only  a  longer  time  than  in  the  first  analysis, 
but  more  intense  heating  as  well.2  If  any  difference  actually  existed,  a 
loss  rather  than  a  gain  was  indicated  in  this  interval. 

To  test  the  effect  of  air  exposure  on  a  rock  powder  which  had  previously 
been  heated  until  the  gas  evolution  had  completely  ceased,  the  exhausted 
powders  of  my  investigation  were  kept  stored  in  paper  bags,  and  several 
of  them  were  reheated  after  intervals  of  some  months.  Two  analyses  of 
the  iron  basalt  from  Ovifak,  Greenland,  made  10  months  apart,  were  as 
follows: 

TABLE  19. 


Analysis 
No.  45. 

Analysis  after 
10  months. 

Hydrogen  sulphide  
Carbon  dioxide 

0.00 
374 

0.00 
1  18 

Carbon  monoxide  
Methane 

1.74 
17 

.30 
03 

224 

04 

Nitrogen  

.16 

.21 

Total  .                   .     . 

805vols 

176vols 

This  basalt  yielded  about  one-third  as  much  carbon  dioxide  after  the 
interval  as  it  did  when  originally  heated,  but  the  hydrogen  in  the  second 
portion  of  gas  was  almost  a  negligible  quantity. 

A  second  test  was  made  with  a  chloritoid  schist  from  the  Black  Hills, 
after  an  interval  of  more  than  a  year. 

1  Sir  James  Dewar,  Proc.  Roy.  Inst..  vol.  11  (1886),  p.  547. 
1  Wright,  A.  W.,  Am.  Jour.  Sci.,  vol.  11  (1876),  p.  262. 


ABSORPTION. 


33 


TABLE  20. 


Analysis 
No.  23. 

Analysis 
a  year  later. 

Hydrogen  sulphide  

0.00 
46 

0.00 
29 

10 

21 

04 

08 

307 

211 

Nitrogen 

05 

Total  

372vols 

269vols 

In  this  case,  hydrogen  has  been  restored  somewhat  more  completely 
than  carbon  dioxide.  Both  of  them  amount  to  approximately  two-thirds 
of  the  original  volume  of  these  gases. 

A  third  test  was  made  with  amphibolite,  after  an  interval  of  four  months. 

TABLE  21. 


Analysis 
No.  94. 

Analysis  four 
months  later. 

Hydrogen  sulphide  
Carbon  dioxide  

0.00 
2.23 

0.00 
.64 

Carbon  monoxide  

1  10 

34 

Methane                 

10 

12 

Hydrogen 

284 

186 

Nitrogen         .     .   . 

13 

09 

Total  

6.40  vols. 

3.05  vols. 

The  recovery  is  here  more  marked  in  the  case  of  hydrogen  than  in  that 
of  carbon  dioxide. 

A  fourth  test  was  made  with  Keweenawan  diabase  from  Houghton, 
Michigan,  after  an  interval  of  six  months. 

TABLE  22. 


Analysis 

No.  85. 

Analysis  6 
months  later. 

Hydrogen  sulphide  
Carbon  dioxide  

0.00 
1.31 

0.00 
1.33 

Carbon  monoxide  
Methane  

.09 
.09 

.08 
.03 

Hydrogen  

2.34 

.43 

Nitrogen      

.05 

.05 

Total 

3  88  vols 

1  92  vols 

After  reposing  six  months  in  a  paper  bag,  this  diabase  gave  as  much 
carbon  dioxide,  when  heated,  as  it  had  in  the  first  combustion;  but  less 
than  one-fifth  as  much  hydrogen  was  evolved  on  the  second  heating. 

It  is  clear  that  an  interval  of  time  partially  restores  the  gas-producing 
properties  of  these  rock  powders.  For  this  phenomenon,  there  are  two 
possible  explanations.  Either  the  first  heating  does  not  expel  all  of  the 
gas  contained  in  the  rock,  which,  by  some  sort  of  diffusion  or  molecular 


34 


THE    GASES    IN    ROCKS. 


rearrangement,  gradually  prepares  itself  to  come  off  when  again  heated,  or 
else  the  rock  powder  absorbs  gases  from  the  atmosphere.  If  the  carbon 
dioxide  were  derived  from  the  decomposition,  at  high  temperatures,  of  a 
carbonate  such  as  that  of  calcium,  the  oxide  of  calcium  thus  produced 
would  be  likely  to  capture  carbon  dioxide  from  the  air,  though  perhaps 
this  would  be  a  slow  process  in  a  paper  bag  where  the  circulation  of  air  was 
comparatively  limited.  Also,  if  the  hydrogen  came  from  chemical  reactions 
between  ferrous  salts  and  water  combined  in  hydrated  minerals,  the  atmo- 
sphere might  have  restored  to  these  minerals  some  of  the  water  which  they 
lost  when  first  heated.  It  was  thought  that  rehydration,  if  combined 
water  be  a  vital  factor  in  the  production  of  hydrogen,  could  be  more  readily 
effected  by  placing  the  exhausted  powder  in  water  for  a  few  days  than  by 
wrapping  it  up  in  a  paper  bag  for  as  many  months. 

Accordingly,  the  Keweenawan  diabase  powder  (No.  85)  which  origin- 
ally gave  3.88  volumes,  and  after  six  months  1.92  volumes,  was  heated  a 
third  time  (a  week  later)  with  the  evolution  of  very  little  gas.  This  powder, 
after  cooling  in  the  vacuum,  was  taken  out  of  the  combustion-tube  and 
immediately  placed  in  a  flask  filled  with  freshly  distilled  water.  A  stopper 
being  fitted  into  the  flask,  it  was  allowed  to  stand  for  66  hours.  At  the 
end  of  this  time,  the  water  was  poured  off,  the  powder  quickly,  but  thor- 
oughly, dried  and  put  into  the  combustion-tube.  When  heated,  this  powder 
gave  off  0.79  volume  of  gas;  but  instead  of  being  largely  hydrogen,  67.72 
per  cent  of  this  was  carbon  dioxide.  Hydrogen  amounted  to  only  14.69  per 
cent,  while  carbon  monoxide  reached  15.06  per  cent.  An  analysis  of  this 

gas  gave: 

TABLE  23. 


Percentages. 

Volumes. 

Carbon  dioxide  

67.72 

0.53 

Carbon  monoxide  
Methane  

15.06 
.19 

.12 
.00 

Hydrogen  .  . 

14.69 

.12 

Nitrogen  

2.34 

.02 

Total 

10000 

79 

This  carbon  dioxide  could  not  have  come  from  the  air,  but  must  have 
existed  within  the  material  and  must  have  withstood  three  successive 
heatings  in  the  combustion-tube.  From  a  comparison  of  these  figures 
with  the  two  previous  analyses  of  the  gas  from  this  material,  what  is  true 
of  the  carbon  dioxide  would  appear  to  be  true  of  the  hydrogen  as  well. 
This  experiment  favors  the  conclusion,  that  the  gas  which  is  obtained  from 
a  rock  powder  by  a  second  heating  after  a  period  of  time,  is  not  due  to  a 
process  of  selective  absorption  from  the  atmosphere,  but  rather  to  changes 
which  have  been  slowly  taking  place  within  the  powder  itself. 

However,  the  results  of  these  experiments  upon  the  absorption  of  gas 
by  rock  powders  at  ordinary  temperatures  and  pressures  can  not  throw 
much  light  upon  the  source  of  the  gases,  or  how  they  came  to  be  embodied 
in  the  rocks,  since  the  conditions  under  which  the  rocks  were  formed  must 
have  been  very  different.  While  high  temperatures,  in  general,  tend  to 


STATES    OF   THE    GASES.  35 

expel  the  gaseous  constituents  of  the  rocks,  high  pressures  would  have  the 
effect  of  promoting  absorption.  Moreover,  it  is  possible  that  molten 
lavas  might  absorb,  or  dissolve,  certain  gases  without  an  increase  of  pres- 
sure. But  the  testimony  of  volcanic  gases  arid  of  the  scoriaceous  surfaces 
of  lava  flows  favors  the  idea  that  gases  and  vapors  are  constantly  being 
boiled  out  of  molten  lavas  whenever  exposed  under  the  ordinary  atmo- 
spheric pressure.  Lavas  give  off  gas  rather  than  absorb  it,  at  the  earth's 
surface;  however,  at  considerable  depths  below  the  surface  the  action  may 
be  entirely  different.  If  the  conception  be  entertained  that  the  earth's 
interior  is,  for  the  most  part,  solid  with  only  threads  of  liquid  lava  here 
and  there,  the  question  for  this  solid  portion  would  be  one  of  the  ability 
of  great  pressure  to  cause  a  solid  to  absorb  gases.  This  need  not  be  further 
dwelt  upon,  since  most  of  the  igneous  rocks  which  are  accessible  have  been 
in  the  liquid  state  at  some  time.  In  the  case  of  the  threads  of  liquid  magma 
there  is  reason  to  suppose  that  gas,  if  it  could  be  brought  into  contact 
with  this  lava,  would  become  incorporated  in  it  owing  to  the  great  pres- 
sure. But  this  does  not  explain  the  original  source  of  the  gases,  nor  how 
they  can  be  brought  in  contact  with  the  liquid  rock  under  the  prevailing 
conditions  of  temperature  and  pressure. 

STATES  IN  WHICH  THE  GASES  EXIST  IN  ROCKS. 

In  order  to  explain  the  immediate  source  of  the  gases  obtained  by 
heating  rock  material  in  vacuo,  three  different  hypotheses  naturally  pre- 
sent themselves.  The  simplest  of  these  is  to  suppose  the  gases  to  exist  in 
minute  cavities  or  pores,  having  been  entrapped  within  the  rock  during  the 
process  of  solidification.  This  supposition  is  suggested  and  supported  by 
the  observation  that  microscopic  slides  of  some  minerals,  notably  quartz 
and  topaz,  reveal  numerous  small  gas-bubbles.  But  while  there  is  evidence 
that  some  gas  is  thus  held  in  cavities,  there  is  equally  strong  evidence  to 
show  that  the  greater  part  of  it  can  not  be  attributed  to  this  source. 

To  escape  the  difficulties  encountered  by  the  first  hypothesis,  appeal 
is  made  to  the  imperfectly  understood  property  of  some  of  the  elements 
to  "occlude,"  or  dissolve  within  their  mass,  certain  gases.  It  is  remem- 
bered that  under  the  proper  conditions  palladium  will  occlude  900  times 
its  own  volume  of  hydrogen,  and  that  the  same  gas  is  also  absorbed,  in 
lesser  degree,  by  other  metals,  particularly  platinum  and  iron,  while  silver 
has  a  similar  affinity  for  oxygen.  This  principle  applied  to  igneous  rocks 
as  a  hypothetical  source  of  their  gases  becomes  at  once  a  more  difficult 
proposition  to  prove  or  disprove. 

The  third  hypothesis,  more  conservative  than  either  of  the  others, 
assumes  that  these  gases  do  not  exist  in  the  rocks  in  the  uncombined,  or 
gaseous  state,  but  are  produced  in  the  combustion-tube  by  chemical  re- 
actions at  high  temperature.  The  oxides  of  carbon  and  sulphur  are  assigned 
to  the  decomposition  of  carbonates  and  sulphates;  methane  to  organic 
matter  present,  carbides,  or  to  high  temperature  reactions  between  hydro- 
gen and  the  carbon  gases;  sulphureted  hydrogen  to  sulphides;  nitrogen 
to  nitrides;  while  hydrogen  is  liberated  from  steam  by  the  action  of  metallic 
iron  or  ferrous  salt. 


THE    GASES   IN    ROCKS. 


GASES  IN  CAVITIES. 

The  studies  of  Brewster,  Davy,  Sorby,  Hartley,  and  others,  have 
established  the  presence  of  gas,  generally  carbon  dioxide,  though  sometimes 
nitrogen,  in  the  minute  cavities  of  certain  crystals.  This  has  been  widely 
known  to  geologists,  and  hence,  when  it  was  discovered  that  many  crystal- 
line rocks  yield  gas  upon  heating  in  vacuo,  it  was  natural  to  suppose  that 
the  gas  came  from  cavities.  Such  was  the  view  taken  by  Tilden.1  But 
while  microscopical  investigations  indicated  that  carbon  dioxide  consti- 
tutes more  than  90  per  cent  of  the  gaseous  matter  inclosed  in  these  cavi- 
ties, and  hydrogen  is  not  found  in  more  than  traces,  the  latter  gas  is  the 
most  important  constituent  of  the  mixture  derived  from  rocks  by  heat. 
In  addition  to  this,  the  observation  that  those  rocks  which  are  not  known 
to  contain  many  gas  cavities  produced  several  times  as  much  gas  as  the 
cavernous  quartzes  also  suggested  that  the  bulk  of  the  gas,  at  least,  could 
not  be  attributed  to  inclosure  in  cavities.  Moreover,  basic  rocks  were 
found  to  be  more  productive  than  acidic,  whereas  it  had  generally  been 
supposed  that  the  latter,  owing  to  their  greater  viscosity,  should  entrap 
more  gas  and  vapor  than  the  more  fluid  basic  lavas. 

The  suspicion  that  the  gas  did  not  come  from  cavities  in  any  large 
degree  was  strengthened  by  the  observation  that  the  composition  of  the 
gas  varied  according  to  the  temperature  to  which  the  rock  powder  was 
heated.  If  the  gas  comes  from  cavities,  its  liberation  should  commence 
with  a  slight  rise  of  temperature  and  should  continue  more  or  less  steadily, 
as  the  heat  increases,  until  the  expansive  force  of  the  gas  opens  up  most 
of  the  pores.  Since  all  gases  expand  equally,  one  should  burst  its  con- 
fines as  soon  as  another,  and  a  sample  of  gas  obtained  at  any  given 
temperature  should  not  differ  very  widely  in  composition  from  that  evolved 
at  any  other. 

Neglecting  hydrogen  sulphide  and  nitrogen,  the  character  of  the  gas 
obtained  at  various  temperatures  from  Baltimore  gneiss  2  is  shown  by  the 
following  table: 

TABLE  24. 


Qas. 

At  360°. 

At  448°. 

At  540°. 

At  600°. 

At  800°. 

At  850°. 

Carbon  dioxide  
Carbon  monoxide  
Methane  

93.7 
6.3 
0.0 

37.5 
4.2 
250 

27.0 
2.4 

18 

13.6 
2.3 
25 

19.3 
2.8 
21 

0.0 

1.1 

34 

Hydrogen  .  . 

0.0 

333 

688 

816 

758 

955 

Total  

10000 

10000 

10000 

10000 

10000 

10000 

Volumes    

03 

03 

128 

140 

530 

94 

Or,  combining  the  separate  analyses  so  that  each  figure  represents  the 
percentage  of  the  total  gas  obtained  up  to  the  specified  temperature,  the 
result  is  as  shown  in  table  25 : 

1  Tilden.  Chem.  News.  vol.  75  (1897),  p.  169:   Proc.  Roy.  Soc.,  vol.  64  (1897),  p.  453. 

2  Material  of  analysis,  No.  28. 


STATES    OF    THE    GASES. 
TABLE  25. 


37 


Gas. 

20°  to  360° 

20°  to  448° 

20°  to  540° 

20°  to  600° 

20°  to  800° 

20°  to  850° 

Carbon  dioxide  .  .  . 
Carbon  monoxide. 
Methane  
Hydrogen  

93.7 
6.3 
0.0 

0.0 

69.7 
5.3 
10.7 
143 

30.1 
2.5 
2.4 
650 

20.2 
2.4 
2.5 

749 

19.5 

2.7 
2.2 
756 

17.5 
2.6 
2.3 

776 

Total  
Volumes  .  .  . 

100.00 
.03 

100.00 
.06 

100.00 
1.34 

100.00 
2.74 

100.00 
8.04 

100.00 
8.98 

Carbon  dioxide  thus  appeared  first,  constituting  93  per  cent  of  the  gas 
evolved  at  360°  C.,  while  hydrogen  was  not  present  in  a  measurable  quan- 
tity. On  the  other  hand,  at  the  highest  temperature  used  (850°)  hydrogen 
amounted  to  95  per  cent  of  the  total  and  carbon  dioxide  was  entirely 
wanting.  The  steady  decrease  in  the  proportion  of  carbon  dioxide  with 
the  elevation  of  the  temperature,  and  the  proportionate  increase  in  the 
value  of  the  hydrogen,  are  striking.  The  minor  constituents,  carbon 
monoxide  and  methane,  underwent  some  variations,  but  did  not  change 
so  radically.  The  former  came  off  at  the  lower  temperature,  but  declined  at 
full  red  heat.  Nitrogen,  it  appears  from  other  experiments,  does  not  appear 
in  the  gases  obtained  by  moderate  heating,  but  increases  steadily  in  impor- 
tance when  the  heat  is  carried  higher.  It  is  the  last  gas  to  be  liberated. 

The  complete  table,  expressing  the  volumes  of  each  gas  per  unit  volume 
of  gneiss,  follows: 


Temperature. 

Has. 

C02. 

CO. 

CH4. 

H2. 

Total. 

100°,  boiling  water  

0.00 
.00 

trace 
trace 
.42 
.18 
.01 
.00 

0.00 
.00 
.03 
.01 
.21 
.17 
1.12 
.00 

0.00 
.00 
tr. 
tr. 
.02 
.03 
.16 
.01 

0.00 
.00 
.00 
.01 
.02 
.03 
.12 
.03 

0.00 
.00 
.00 
.01 
.54 
1.02 
4.39 
.86 

0.00 
.00 
.03 
.03 
1.28 
1.40 
5.30 
.94 

218°,  boiling  naphthalene  
360°,  boiling  anthracene  

448°  boiling  sulphur  

540°  metal  bath  

600°  dull  red  heat 

800°  full  blast 

850°  forced  heat 

Total 

.61 

1.54 

.22 

.20 

6.82 

8.98 

These  results  are  graphically  represented  in  the  curves  of  figure  1. 

The  fact  that  little  gas  could  be  obtained  below  450°  is  in  itself  a  strong 
argument  against  the  hypothesis  that  the  gases  come  from  pores,  and 
there  also  seems  no  way  in  which  the  behavior  of  the  gases,  as  set  forth  by 
these  curves,  can  be  consistently  fitted  into  that  theory. 

TESTIMONY    OF   THE    METEORITES. 

Meteorites  have  already  been  subjected  to  investigation  of  this  sort, 
though  not  with  this  purpose  in  mind.  Mallet  divided  the  gas  which  he 
extracted  from  the  meteoric  iron  of  Augusta  County,  Virginia,  into  three 
portions;1  his  results  have  been  reduced  by  Wright2  to  the  figures  given 
in  table  27: 

1  Mallet,  Proc.  Roy.  Soc.,  vol.  20,  p.  367.        2  Wright,  Am.  Jour.  Sci.,  vol.  2,  p.  261. 


38 


THE    GASES   IN    ROCKS. 
TABLE  27. 


C02. 

CO. 

H2. 

N,. 

Beginning  

15.09 

30.74 

42.52 

11.65 

4.23 

46.12 

43.64 

6.01 

End  

369 

47.00 

13.36 

35.95 

The  analyses  of  meteorites  by  Wright  show  that,  in  all  cases,  carbon 
dioxide  reached  a  higher  percentage  in  the  gas  evolved  at  500°  than  it 
did  in  that  obtained  at  red  heat,  and  that  the  reverse  of  this  was  true  of 
hydrogen  in  the  stony  meteorites.  In  the  iron  meteorites,  however,  two 
analyses  indicated  a  marked  fall  in  hydrogen  with  the  increase  of  heat,  while 
the  other  two  were  characterized  by  an  increase.  Wright's  figures  for  the 
meteorite  from  Guernsey  County,  Ohio,  illustrate  the  continuous  decrease 
in  the  percentage  of  carbon  dioxide:  At  100°,  95.92  p.  ct.;  at  250°,  86.36  p. 
ct.;  at  500°,  82.28  p.  ct.;  incipient  red  heat,  33.55  p.  ct.;  red  heat,  19. 16 p.  ct. 

The  volume  of  gas  obtained  at  each  temperature  is  only  stated  for 
500°  and  red  heat.  These  show  that  up  to  500°,  2.06  volumes  were  evolved, 
and  that  above  this  point  only  0.93  volume  was  received.  From  this  it 
appears  that  the  diminishing  percentages  of  carbon  dioxide  above  500° 
represent  an  absolute  slackening  of  the  output  of  that  gas,  as  well  as  an 
apparent  decrease  due  to  the  greater  evolution  of  hydrogen.  It  might 
be  argued  that  in  this  case,  where  gas  was  produced  at  only  100°,  the 
cavities  contributed  the  carbon  dioxide,  yielding  it  early  and  then  slacken- 
ing, as  would  be  expected;  but  even  if  this  be  admitted,  the  hydrogen 
manifestly  can  not  be  ascribed  to  that  source.  Tending  in  a  measure  to 
support  this  view  is  the  work  of  Sorby,1  who  has  shown  that  olivine  crystals 
in  the  meteorites  of  Aussun  and  Parnallee,  when  examined  under  the  micro- 
scope, contain  numerous  small  cavities  filled  with  gas,  similar  to  those  which 
have  been  observed  in  many  terrestrial  minerals. 

In  his  earlier  paper,  Wright  expressed  the  opinion  that  the  gases  were 
partly  condensed  upon  the  particles  of  iron  and  partly  absorbed  within 
them.  Later  he  took  the  position  that  while  some  gas  may  be  condensed 
upon  the  fine  particles  of  iron,  a  large  part  of  the  carbon  dioxide,  and  prob- 
ably also  of  the  other  gases,  is  mechanically  imprisoned  in  the  substance  of 
the  meteorite.  This  view,  which  does  not  seem  to  be  in  accord  with  his 
researches  at  different  temperatures,  he  bases  largely  upon  a  single  experi- 
ment. Material  from  the  Iowa  meteorite  was  finely  pulverized  and  the 
iron  grains  separated  from  the  non-metallic  powder.  A  third  portion 
consisted  of  coarse  fragments  of  the  meteorite.  The  three  portions  heated 
for  the  same  time  gave  the  following  results: 

TABLE  28. 


COS+CO. 

H2. 

N2. 

Volumes. 

Powder  
Iron  

66.96 
3872 

30.96 
5938 

2.08 
190 

°-97  llAH 

051  11'48 

Fragments 

4807 

5093 

100 

1  87 

1  Sorby,  Proc.  Roy.  Soc.,  vol.  13  (1864),  pp.  333-334. 


STATES    OF   THE    GASES. 


The  greater  volume  of  gas  from  the  fragments  was  taken  to  indicate 
that  a  portion  of  the  gas  was  lost  in  the  process  of  pulverization.  An 
analysis  of  these  figures  reveals  the  fact  that  the  difference  in  volume 
was  chiefly  due  to  the  deficiency  of  the  combined  portions  in  hydrogen, 
instead  of  carbon  dioxide,  and  that  while  there  was  also  a  slight  loss  of 
the  latter  gas,  there  was  a  decided  gain  in  nitrogen. 

Returning  to  the  rocks,  Tilden  1  is  authority  for  the 
statement  that  it  does  not  make  much  difference  in  the 
quantity  of  gas  evolved,  whether  the  material  be  taken 
in  chunks  or  in  a  fine  powder.  Instead  of  abandoning 
the  idea  of  cavities,  he  believed  them  to  be  very  minute. 
But  this  is  approaching  an  alternative  hypothesis;  if 
the  reduction  of  the  cavities  is  carried  far  enough  —  to 
intermolecular  spaces  —  practical  occlusion  is  the  result. 

Another  objection  to  the  theory  of  mechanically-re- 
tained gases  apparently  exists  in  the  slowness  with  which 
the  gas  is  liberated  when  the  material  is  heated.  Usually 
about  three  hours  and  often  a  very  much  longer  time  is 
required  to  expel  the  gas.  Unless  the  gas  from  cavities 
be  assumed  to  escape  by  diffusion  through  the  walls  of 
the  inclosing  mineral,  instead  of  violently  bursting  its 
confines,  there  is  no  reason  why  it  should  not  come  off 
with  a  rush  when  the  combustion-tube  is  heated  rapidly 
to  redness.  Some  rocks,  generally  those  yielding  a  mod- 
erate quantity  of  gas  in  which  carbon  dioxide  is  the 
principal  constituent,  often  give  up  their  gas  quickly  — 
mostly  within  the  first  60  to  90  minutes,  although  the 
generation  continues  for  a  longer  time,  before  ceasing 
altogether.  But  other  varieties  of  rock,  particularly 
those  noted  for  greater  volumes,  in  which  the  percent- 
age of  hydrogen  runs  high,  emit  gas  slowly  and  steadily 
for  three  or  four  hours. 

These  considerations  led  me  to  try  a  series  of  experi- 
ments which  should  show  how  much  gas  actually  could 
be  obtained  from  the  opening  of  cavities  alone.  For  this 
purpose  a  crusher  was  devised  (fig.  2),  capable  of  pulver- 
izing a  rock  specimen  in  a  complete  vacuum.  Adopt- 
ing  the  principle  of  the  familiar  steel  mortar,  this  was 
constructed  in  three  pieces.  The  cylindrical  cup  in 
which  the  rock  material  is  crushed  possesses  an  internal  diameter  of  7 
centimeters  and  a  depth  of  9  centimeters.  The  walls  are  purposely 
made  thick  and  strong  and  the  bottom  is  protected  from  the  abrasion  of 
hard  minerals  by  inserting  a  disk  of  hardened  steel.  Inserted  in  the  walls 
is  a  stopcock  through  which  the  apparatus  is  to  be  exhausted  and  the 
gases  later  pumped  out.  A  circular  steel  cap,  or  cover,  provided  with  six 
screws,  whose  sockets  are  depressed  in  the  top  of  the  cylinder,  is  intended 
to  make  the  chamber  of  the  mortar  air-tight.  In  the  center  of  the  cap- 

1  Tilden,  Chem.  News,  vol.  75  (1897),  p.  169;  Proc.  Roy.  Soc.,  vol.  64  (1897),  p.  453. 


V 

t 


FIG.  2.—  Apparatus  for 
specimena 


40  THE    GASES    IN   ROCKS. 

piece  is  a  hole  large  enough  to  permit  the  ready  movement  of  the  piston- 
shaft.  Around  this  hole  on  the  upper  side  there  is  welded  a  short  piece  of 
steel  tubing  which  is  to  guide  the  piston-rod  and  serve  as  a  place  of  attach- 
ment for  the  rubber  tubing  in  which  the  shaft  of  the  piston  is  incased. 
The  piston  is  a  shaft  50  centimeters  in  length,  2.2  centimeters  in  thickness, 
to  which  is  attached  a  head  piece  of  hardened  steel  which  will  fit  snugly 
into  the  cylinder.  Near  the  upper  end  of  the  piston  is  a  cross-bar  serving 
as  a  handle,  and  also  a  flange  to  which  the  rubber  tube  is  to  be  fitted. 

When  ready  to  put  together,  the  piston-shaft  is  incased  in  a  1-inch 
tube  of  pure  rubber,  45  centimeters  long,  which  is  tightly  fitted  and  wired 
to  the  flange  near  the  end  of  the  rod,  whereupon  the  other  end  of  the  shaft 
is  slipped  through  the  hole  in  the  cover-piece,  and  the  piston-head  affixed. 
The  lower  end  of  the  rubber  tube  is  wired  to  the  steel  tube  of  the  cover- 
piece  which,  after  the  rock  specimen  has  been  placed  in  the  cylinder,  is 
fitted  with  a  rubber  washer  and  screwed  as  tightly  as  possible  to  the  cylinder. 
The  rubber  tube  is  taken  of  length  sufficient  to  allow  the  head  of  the  piston 
to  touch  the  bottom  of  the  cylinder;  by  pulling  upward  on  the  handle  the 
rubber  wrinkles  and  folds  upon  itself,  affording  ample  play  to  the  piston. 

The  stopcock  is  connected  with  the  mercury-pump  and  the  cylinder  of 
the  crusher  exhausted,  after  which  vigorous  strokes  delivered  at  the  end  of 
the  piston  with  a  heavy  mallet  crush  the  rock,  thus  opening  the  gas  cavities. 
Whatever  gas  is  liberated,  is  pumped  into  the  receiver  and  analyzed  in  the 
ordinary  way. 

RESULTS. 

Of  the  first  rock  tested,  a  basalt  from  the  Faroe  Islands,  42  grams 
were  crushed  finely  enough  to  pass  through  a  30-mesh  sieve,  besides  several 
times  as  much,  less  completely  pulverized.  In  all,  less  than  0.1  cubic 
centimeter  of  gas  was  obtained,  which  may  be  considered  as  practically  no 
gas  at  all,  since  this  small  quantity  is  within  the  leaking  possibilities  of  the 
apparatus. 

A  slightly  scoriaceous  basalt  from  Hawaii  produced  about  0.1  cubic 
centimeter  of  gas,  which  appeared  to  be  largely  air.  No  carbon  dioxide 
could  be  detected.  Of  this  basalt,  18.3  grams  passed  through  the  sieve. 

15.73  grams  of  vein  quartz  from  Utah  (No.  71  of  the  analyses)  gave  no 
trace  of  gas. 

In  an  effort  to  demonstrate  conclusively  that  the  lack  of  gas  liberated 
by  crushing  these  lavas  was  not  due  to  defective  apparatus,  a  glass  bulb 
of  measured  capacity,  filled  with  air,  was  broken  in  the  crusher  in  place  of 
the  rock  ordinarily  used.  The  result  showed  that  gas  introduced  into  the 
crusher  can  be  extracted  without  sensible  change  in  volume.  As  diffusion 
through  the  rubber  tubing  was  considered  a  possible,  though  not  very 
probable,  source  of  error,  a  further  trial  was  made,  using  hydrogen,  lightest 
and  most  active  among  the  gases,  in  order  to  put  the  apparatus  to  as 
severe  a  test  as  possible.  The  purity  of  this  hydrogen  had  previously  been 
established  by  analysis.  The  bulb  broken,  the  gas  was  pumped  off  and 
exploded  with  air.  The  observed  shrinkage  agreed,  within  the  limit  of 
error,  with  the  amount  of  hydrogen  calculated  to  have  been  contained 
within  the  bulb. 


STATES    OF  THE    GASES.  41 

Being  desirous  of  finding  some  specimen  which  would  yield  gas  when 
crushed  in  this  manner,  I  procured  some  crystals  of  cavernous  quartz 
from  Porretta,  Italy,  in  which  several  of  the  cavities  exceeded  a  millimeter 
in  diameter.  5.91  grams  were  crushed  to  sufficient  fineness  to  pass  through 
the  sieve,  and  61.66  grams  were  partially  crushed.  0.08  cubic  centimeter 
of  carbon  dioxide  was  obtained,  which,  supposing  that  it  all  came  from  the 
5.91  grams,  would  be  equivalent  to  only  0.03  of  the  volume  of  the  quartz. 
An  analysis  showed  also  a  little  methane  and  some  nitrogen,  but  the  amount 
of  gas  available  was  too  small  for  the  determination  to  be  of  any  value. 

The  result  of  this  last  test  agrees  with  the  microscopic  studies  of  the 
early  investigators.  Carbon  dioxide  exists  in  the  cavities  of  quartz,  but 
its  volume,  compared  with  the  volume  of  the  inclosing  mineral,  is  small. 
Microscopical  observations  seem  to  show  that  gas  cavities  occur  almost 
exclusively  in  a  certain  set  of  minerals  which  combine  hardness  usually  with 
imperfect  cleavage,  namely,  quartz,  topaz,  garnet,  spinel,  beryl,  chrysoberyl, 
corundum  in  the  form  of  rubies,  sapphires,  and  emeralds,  and  diamond. 
These  are  minerals  which,  once  they  had  inclosed  gas,  would  hold  it,  even 
under  great  pressure. 

GASES  DUE  TO  CHEMICAL  REACTIONS. 

HYDROGEN. 

The  double  series  of  iron  salts,  ferrous  and  ferric,  together  with  the 
intermediate  ferroso-ferric  compounds,  reacting  with  oxidizing  or  reducing 
agents,  undergo  various  reversible  reactions  whose  possibilities  are  great. 
When  steam  is  passed  over  metallic  iron  or  ferrous  oxide  at  a  red  heat,  it 
is  decomposed,  giving  up  oxygen  to  the  iron,  and  at  the  same  time  pro- 
ducing free  hydrogen.  The  reactions  may  be  written: 

Fe  +  H2O  =  FeO  +  H2  3FeO  +  H2O  =  Fe3O4  +  H2 

Hydrogen  is  produced  in  this  way  most  rapidly  at  temperatures  about 
500°.  Stromeyer  is  authority  for  the  statement  that  the  breaking  up  of 
water  begins  at  150°  but  takes  place  very  slowly;  at  200°  somewhat  more 
rapidly;  at  360°  the  process  requires  several  hours;  at  860°  it  is  complete 
in  less  than  one  hour;  while  near  the  melting-point  of  iron  several  minutes 
are  sufficient.1 

The  authorities  agree  that  ferric  oxide  is  not  formed  in  this  process; 
the  magnetic  oxide,  Fe3O4  is  the  final  product  of  the  action  of  a  current 
of  steam  upon  ferrous  oxide.2 

But  these  reactions  are  completely  reversible.  According  to  Gay- 
Lussac,  magnetite  is  reduced  to  the  metal  by  hydrogen  at  every  tempera- 
ture between  400°  and  the  highest  degree  of  heat  obtainable  in  the  com- 
bustion-furnace, particularly  at  the  same  temperature  at  which  steam  is 
split  up  by  glowing  iron.3  Siewert  states  that  ferric  oxide  (from  the  oxa- 
late)  is  not  altered  by  hydrogen  at  270°  to  280°;  between  280°  and  300° 

1  Stromeyer,  Pogg.  Ann.,  vol.  9,  p.  475. 

2  Among  others,  Regnault,  Ann.  de  Chim.  et  Phys.,  vol.  62,  p.  346. 
8  Gay-Lussac,  Ann.  de  Chim.  et  Phys.,  vol.  1,  p.  33. 


42  THE    GASES   IN    ROCKS. 

it  is  reduced  to  ferrous  oxide,  and  when  heated  above  300°,  to  the  metal.1 
The  more  recent  studies  of  Moissan  give  different  figures;2  Fe2O3  is  reduced 
by  hydrogen  at  300°  to  Fe304  in  30  minutes;  at  500°  to  FeO  in  20  minutes; 
at  600°  to  700°  to  metallic  iron. 

If  the  hydrogen  or  water-vapor  produced  by  these  reactions  is  not 
removed,  the  process  continues  only  until  a  condition  of  equilibrium  is 
established.  In  extracting  the  gases  from  rocks,  the  products  of  these 
reactions  were  rapidly  removed,  so  that  final  equilibrium  was  probably 
never  attained.  Hence,  in  these  experiments  the  direction  in  which  the 
reaction  will  proceed  depends  upon  whether  there  is  ferrous  oxide  and 
water,  or  ferric  oxide  and  hydrogen,  most  abundantly  stored  in  the  rock. 
Ferrous  and  ferric  salts  behave,  in  general,  like  the  oxides. 

Since  most  igneous  rocks  contain  ferrous  as  well  as  ferric  salts,  the 
possibility  that,  when  heated  in  the  presence  of  steam,  hydrogen  will  be 
produced,  must  always  be  taken  into  account.  In  terrestrial  rocks  water 
of  constitution  is  generally  present  and  often  is  not  expelled  below  a  bright 
red  heat.  Thus,  a  rock  containing  a  ferrous  compound  in  appreciable 
amount,  together  with  water  of  crystallization,  a  portion  of  which  is  re- 
tained up  to  red  heat,  will  be  in  a  condition  to  furnish  hydrogen  upon  the 
application  of  heat. 

In  general,  the  analyses  show  that  the  greater  the  amount  of  iron  present 
in  the  rock,  the  more  hydrogen  may  be  expected.  This  may  be  the  result 
of  chemical  action,  or  a  selective  occlusion  of  hydrogen  manifested  by  iron 
and  its  compounds.  Magnetite,  being  the  end  product  of  the  reaction  of 
water  upon  iron,  can  not  produce  hydrogen  by  this  chemical  interaction, 
though  it  might  possess  the  occlusive  properties  of  iron  compounds.  Anal- 
ysis of  the  black  sand  from  the  bed  of  the  Snake  River,  Idaho,3  indicates 
that  iron  in  the  form  of  magnetite  does  not  yield  much  hydrogen.  How- 
ever, these  figures  have  no  great  significance,  for,  even  though  an  abundance 
of  hydrogen  existed  in  the  ore,  either  occluded  or  mechanically  imprisoned, 
the  magnetite  would,  at  red  heat,  quickly  oxidize  it  to  water,  with  the 
exception  of  a  small  portion  of  free  hydrogen  maintained  by  the  reverse 
reaction.  The  analyses  show  that  basic  diabases  and  basalts  yield  the 
most  gas,  while  acidic  rhyolites  give  but  little.  These  are  also  among  the 
maximum  and  minimum  iron-bearing  lavas.  But  the  difference  in  hydro- 
gen is  much  greater  proportionately  than  the  difference  in  ferrous  salts. 
Table  13 4  also  shows  that  andesites,  which  are  nearer  the  basic  end  of  the 
scale  than  the  acidic,  do  not  greatly  exceed  the  rhyolites  in  hydrogen. 
The  difference  between  the  two  types  of  rocks,  acidic  and  basic,  in  point 
of  volume  of  the  individual  gases,  while  somewhat  more  conspicuous  in 
the  case  of  hydrogen,  is  generally  true  of  the  other  gases  as  well. 

Endeavoring  to  prove  that  the  hydrogen  obtained  by  heating  minerals 
came  entirely  from  chemical  reactions,  Travers  experimented  with  the 
secondary  mineral  chlorite,  calculating  how  much  ferrous  iron  should  have 
been  oxidized  to  give  the  quantity  of  hydrogen  and  carbon  monoxide 
evolved.5  This  he  found  to  agree  closely  with  the  difference  in  amount  of 

1  Siewert,  Jahresbericht  d.  Chem.,  1864,  p.  265.      4  Ante,  p.  27. 

2  Moissan,  Comptes  Rendus,  vol.  84,  p.  1296.       5  Travers,  Proc.  Roy.  Soc.,  vol.  64,  p.  132. 
'Analysis  No.  46. 


STATES    OF   THE    GASES. 


43 


ferrous  iron  present  before  and  after  heating.  Another  test  with  feldspar 
from  the  Peterhead  granite  not  showing  correspondence,  seemed  to  Travers 
to  be  explained  by  the  presence  of  both  metallic  iron  and  ferrous  oxide  in 
the  feldspar.  The  presence  of  a  considerable  amount  of  metallic  iron  in 
a  feldspar  which  crystallized  from  an  acidic  magma  containing  an  excess 
of  silica  is  quite  unusual.  This  feldspar  treated  with  dilute  sulphuric 
acid  yielded  about  four  volumes  of  hydrogen. 

Against  the  theory  that  the  hydrogen  was  largely  derived  from  the 
action  of  water-vapor  on  ferrous  compounds,  may  be  placed  the  very 
marked  change  in  color  which  the  rock  undergoes  during  the  process  of 
heating.  I  have  observed  that  whenever  a  rock  powder,  before  being 
placed  in  the  tube,  possesses  an  orange,  brownish,  or  reddish  tint  due  to 
ferric  oxide,  the  combustion  invariably  alters  the  tone  to  a  greenish  gray. 
This  suggests  a  reduction  of  ferric  oxide  to  ferrous  oxide,  a  process  con- 
suming hydrogen.  In  order  to  test  this  question,  a  specimen  of  bright-red 
Permian  sandstone  from  the  Garden  of  the  Gods  near  Colorado  Springs 1 
was  powdered.  These  Red  Beds  are  supposed  to  consist  of  thoroughly 
oxidized  material;  this  opinion  was  partially  confirmed  by  chemical  tests 
which  gave  a  weak  reaction  for  ferrous  iron,  but  indicated  much  ferric. 
After  heating,  the  brick-red  sand  had  become  dull  gray-green  in  color.  The 
gray  sand  from  the  combustion-tube  gave  a  stronger  reaction  for  fer- 
rous iron.  Later,  a  quantitative  determination  of  the  ferrous  iron  present 
before  and  after  heating  was  undertaken.  Equal  weights  of  the  two  sands 
were  boiled  with  strong  sulphuric  acid  2  for  two  hours  and  then  allowed  to 
stand  overnight.  In  each  case  the  solution  was  effected  in  an  atmosphere 
of  carbon  dioxide  to  prevent  oxidation  by  oxygen  from  the  air.  The  two 
solutions  were  then  titrated  with  potassium  permanganate  solution.  3.09 
grams  red  sand  required  1.97  cubic  centimeters  N/10  KMnO4;  3.09  grams 
gray  sand  required  2.52  cubic  centimeters  N/10  KMnO4.  0.55  cubic  centi- 
meter N/10  KMnO4  is  equivalent  to  0.015  gram  of  iron,  which  is  the 
weight  of  the  metal  reduced  from  the  ferric  to  the  ferrous  state.  For  the 
total  weight  of  sand  used  in  the  gas  analysis  (85  grams),  the  increase  in 
ferrous  iron  should  be  0.423  gram,  which  would  correspond  to  an  oxidation 
of  approximately  85  cubic  centimeters  of  hydrogen.  Yet  both  hydrogen 
and  carbon  monoxide  were  obtained  from  this  sandstone  in  considerable 
quantities. 

TABLE  29. 


Per  cent. 

Volumes. 

Hydrogen  sulphide  .  . 

005 

000 

Carbon  dioxide 

carbonated 

Carbon  monoxide  
Methane             

60.69 
627 

.71 
07 

Hydrogen 

2728 

32 

Nitrogen  

5.71 

.06 

Total  

100.00 

1.16 

1  Analysis  No.  78. 

2  3  parts  cone,  acid  to  1  part  water. 


44 


THE    GASES   IN   ROCKS. 


In  order  to  ascertain  the  quantitative  effect  of  the  presence  of  ferric 
oxide  in  moderate  amount,  0.77  gram  of  pure  Fe2O3  was  mixed  with  20.04 
grams  of  diabase  powder,  tinting  this  latter  a  reddish  brown.  An  analysis 
of  the  resulting  gas  and  of  the  original  diabase  gave  the  figures  shown  in 
the  following  table: 

TABLE  30. 


Resulting  gas. 

Original  diabase.* 

Per  cent. 

Volumes. 

Per  cent. 

Volumes. 

0.06 
72.99 
3.90 
.87 
20.79 
1.39 

0.00 
7.08 
.38 
.09 
2.01 
.13 

Hydrogen  sulphide  
Carbon  dioxide  
Carbon  monoxide  
Methane 

0.04 
61.25 
2.47 
1.32 
33.69 
1.23 

0.00 

8.51 
.34 
.18 
4.68 
.17 

Carbon  dioxide  

Aiy  uiufccii  

Total  

Total  

100.00 

9.69 

100.00 

13.88 

1  Analysis  No.  86. 

A  comparison  of  these  results  shows  that,  while  the  yield  of  hydrogen 
was  diminished  by  the  ferric  oxide  to  less  than  half  of  what  it  would  have 
been,  the  carbon  monoxide  was  not  affected.  The  ferric  oxide  apparently 
only  went  down  to  a  state  of  equilibrium,  and  was  not  in  sufficient  quantity 
to  offset  the  copious  evolution  of  hydrogen  from  the  diabase.  The  brown 
color,  however,  was  replaced  by  green. 

To  get  rid  of  the  iron,  and  particularly  ferrous  iron,  material  from  the 
same  diabase  specimen  was  treated  with  concentrated  nitric  acid  for  66 
hours.  Much  gas  came  off  at  first,  nitric  oxide,  perhaps  from  the  action 
of  the  acid  on  pyrite,  being  very  conspicuous.  The  powder,  washed  repeat- 
edly on  a  filter  until  all  the  acid  had  been  removed,  was  dried  in  an  oven 
overnight  and  then  heated  at  115°  in  an  air-bath  for  half  an  hour.  Two 
and  a  half  hours  at  red  heat,  in  vacuo,  then  expelled  only  0.23  volume  of 
gas  from  the  diabase  powder.  Its  composition  is  given  in  table  31. 

TABLE  31. 


Per  cent. 

Volumes. 

Hydrogen  sulphide  

0.00 

0.00 

Carbon  dioxide  

25.23 

.06 

Carbon  monoxide  

20.15 

.05 

636 

01 

Hydrogen  

21.21 

.05 

2705 

06 

Total 

10000 

23 

A  similar  test  was  made  with  dilute  sulphuric  acid,  in  a  vacuum.  In 
this  experiment,  the  gas  driven  off  by  the  acid  during  the  first  2J  hours 
was  collected  and  analyzed.  Table  32  shows  this  to  have  been  chiefly 
carbon  dioxide. 


STATES   OF  THE   GASES. 
TABLE  32. 


45 


Per  cent. 

Volumes. 

Hydrogen  sulphide  

0.00 

0.00 

Carbon  dioxide 

9810 

644 

Carbon  monoxide  \ 

.03 

00 

Methane                 /  '  ' 
Hydrogen               

25 

02 

Nitrogen  

1.62 

.10 

Total  

100.00 

6.56 

As  a  precautionary  measure,  to  avoid  the  introduction  of  any  metallic 
iron  in  the  process  of  pulverization,  the  diabase  was  reduced  to  a  powder 
in  an  agate  mortar.  The  brass  sieve  was  not  used.  Hence  this  hydrogen 
did  not  come  from  any  action  of  the  acid  upon  a  metal  introduced  during 
the  manipulations. 

This  powder,  after  remaining  in  a  vacuum  with  an  excess  of  sulphuric 
acid  for  three  days,  was  washed  thoroughly  on  a  Gooch  filter  until  the  last 
traces  of  calcium  sulphate  had  been  removed.  After  drying  for  an  hour 
at  125°,  the  powder  was  placed  in  the  combustion-tube  and  heated  to 
redness.  The  sulphuric  acid  left  more  gas  in  the  rock  than  the  nitric. 

TABLE  33. 


Per  cent. 

Volumes. 

1330 

021 

Carbon  dioxide  

38.19 

.62 

Carbon  monoxide  
Methane  

9.01 
395 

.14 
.06 

Hydrogen  

3380 

.54 

Nitrogen  

1.75 

.03 

Total 

10000 

160 

From  these  experiments  it  would  appear  that  acids  remove  the  critical 
gas-producing  factors  without  liberating  a  notable  amount  of  any  gas 
except  carbon  dioxide.  Whether  hydrogen  may  not  pass  into  solution 
with  the  iron,  without  being  freed,  is  a  question  which  naturally  arises, 
but  the  balance  of  chemical  opinion  is  against  this  supposition. 

Professor  Dewar  digested  celestial  graphite  in  strong  nitric  acid  for 
several  hours  and,  after  washing  and  drying,  found  that  with  heat  it  gave 
exactly  the  same  amount  of  hydrogen  as  before  treating  with  the  acid. 
This  would  suggest  that,  in  the  case  of  celestial  graphite,  the  hydrogen 
was  not  connected  with  iron,  but  existed  in  some  very  stable  form.1 

If  all  the  hydrogen  was  produced  by  the  reaction  of  water  on  ferrous 
salts,  it  would  seem  as  if  the  volume  obtained  should  bear  a  direct  relation 
to  the  quantity  of  these  two  critical  constituents  present  in  the  rock. 
To  throw  light  on  this  matter,  two  rocks  of  the  same  origin,  but  of  different 
chemical  composition,  presented  the  most  favorable  line  of  attack.  An 
intrusive  andesite  and  a  specimen  of  vein  quartz  derived  from  the  mag- 

1  Dewar,  Proc.  Roy.  Inst.,  vol.  11,  p.  550. 


46 


THE    GASES   IN    ROCKS. 


matic  waters  of  the  intrusion,  kindly  furnished  by  Dr.  C.  K.  Leith,  were 
used  to  illustrate  this  point.1  Though  containing  very  different  quantities 
of  ferrous  compounds,  they  yielded  identical  volumes  of  methane,  hydrogen, 
and  nitrogen.  These  analyses  are  given  in  table  34. 

TABLE  34. 


Andesite. 

Vein  quartz. 

Per  cent. 

Volumes. 

Per  cent. 

Volumes. 

Hydrogen  sulphide  
Carbon  dioxide  
Carbon  monoxide  
Methane  

0.03 

77.50 
4.75 
.95 
15.35 
1.42 

0.00 
2.66 
.16 
.03 
.53 
.05 

Hydrogen  sulphide  
Carbon  dioxide  
Carbon  monoxide  
Methane  .  . 

0.00 
13.93 
11.26 
4.00 
64.40 
6.41 

0.00 

.11 

.09 
.03 
.53 
.05 

Hydrogen  

HydrogenT  .  .  . 

Nitrogen  

Nitrogen  

Total 

Total  

100.00 

3.43 

100.00 

.81 

The  great  excess  of  carbon  dioxide  in  the  andesite  is  assigned  to  car- 
bonation  of  that  lava  subsequent  to  its  formation — a  process  to  which  the 
quartz  would  not  be  susceptible. 

The  observation  that  comparatively  pure  quartz  yielded  half  a  volume 
of  hydrogen  suggested  a  quantitative  analysis  to  determine  the  amount 
of  iron  actually  contained  in  hydrogen-producing  quartz.  For  the  purpose 
quartz  from  Orange,  New  South  Wales,  was  selected.  102.72  grams  of  the 
quartz  yielded  4.81  cubic  centimeters  of  hydrogen  at  0°  and  760  millimeters.2 
After  the  gas  had  been  extracted,  two  different  portions  of  the  exhausted 
mineral  were  digested  with  aqua  regia — one  of  them  boiled  for  an  hour, 
the  other  being  allowed  to  stand  during  several  days,  and  occasionally 
warmed  to  the  boiling-point.  The  acid  may  be  considered  to  have  dis- 
solved all  the  iron  from  which  gas  could  have  escaped.  To  make  the  case 
certain,  all  of  the  iron  detected  has  been  supposed  to  have  existed  in  the 
quartz  as  ferrous  oxide,  although  some  of  it  undoubtedly  occurred  in  the 
form  of  ferric  compounds.  The  iron  was  weighed  as  Fe2O3. 

First  determination: 

22.22  gins,  quartz  contained 0.0015    gm.  Fe2O3 

102.72  gins,  quartz  would  contain 00693  gm.  Fe2O$ 

102.72  gms.  quartz  would  contain 00485  gm.  Fe 

Fe  (as  FeO)  required  to  give  1  c.c.  hydrogen 00748  gm. 

Maximum  amount  hydrogen  from  reaction 65  c.c. 

Hydrogen  actually  obtained  (at  0°  and  760  mm.) 4.81  c.c. 

Hydrogen  not  from  this  reaction 4.16  c.c. 

Second  determination: 

52.02  gms.  quartz  contained 0.0042    gm.  Fe2Os 

102.72  gms.  quartz  would  contain 00829  gm.  Fe2O, 

102.72  gms.  quartz  would  contain 00580  gm.  Fe 

Fe  (as  FeO)  required  to  give  1  c.c.  hydrogen 00748  gm. 

Maximum  amount  hydrogen  from  reaction 77  c.c. 

Amount  of  hydrogen  actually  obtained 4.81  c.c. 

Hydrogen  not  from  this  reaction 4.04  c.c. 

1  Analyses  Nos.  70  and  71. 

'  Analysis  No.  100. 


STATES    OF    THE    GASES.  47 

According  to  these  two  determinations,  this  quartz  evolved  respectively 
7.4  or  6.2  times  as  much  hydrogen  as  could  have  been  generated  by  the 
reaction  3FeO  +  H2O  =  Fe3O4  +  H2. 

If  the  iron  existed  as  pyrite,  four  times  as  much  hydrogen  as  could 
come  from  ferrous  oxide  might  have  been  produced  in  accordance  with 
the  equation 

3FeS2  +  4H20  =  Fe3O4 


On  the  basis  of  this  equation  the  excess  of  hydrogen  from  the  quartz 
is  much  reduced. 

First  determination: 

102.72  gms.  quartz  contain  ..............................  0.00485  gm.  Fe 

Fe  (as  FeS2)  required  to  give  1  c.c.  hydrogen  ...............  00187  gm. 

Hydrogen  possible  from  reaction  .........................   2.60  c.c. 

Hydrogen  actually  obtained  .............................  4.81  c.c. 

Hydrogen  not  from  this  reaction  .........................   2.21  c.c. 

Second  determination: 

102.72  gms.  quartz  contain  ..............................  0.00580  gm.  Fe 

Fe  (as  FeS2)  required  to  give  1  c.c.  hydrogen  ................  00187  gm. 

Hydrogen  possible  from  reaction  .........................   3.08  c.c. 

Hydrogen  actually  obtained  .............................   4.81  c.c. 

Hydrogen  not  from  this  reaction  ..........................    1.73  c.c. 

These  computations  assume  not  only  that  all  the  iron  in  the  quartz 
was  combined  as  pyrite,  and  that  it  was  completely  oxidized  to  magnetite, 
but  that  the  hydrogen  sulphide  produced  was  entirely  dissociated  into 
hydrogen  and  sulphur.  But  the  iodine  titration  in  the  gas  analysis  revealed 
0.36  cubic  centimeter  (at  0°  and  760  millimeters)  of  sulphur  gas  whose 
odor  was  that  of  hydrogen  sulphide  rather  than  sulphur  dioxide.  If  this 
were  H2S,  it  would  diminish  the  amount  of  hydrogen  which  could  have  come 
from  the  reaction  by  0.36  cubic  centimeter;  if,  however,  it  were  sulphur 
dioxide  the  volume  of  possible  hydrogen  would  be  swelled  by  0.72  cubic 
centimeter  in  accordance  with  the  reaction 

S  +  2H2O  =  SO2  +  2H2 

But  as  there  was  certainly  much  more  hydrogen  sulphide  than  sulphur 
dioxide  absorbed  by  the  potassium  hydroxide  solution,  it  will  be  safe  to 
balance  the  possible  SO2  formed,  by  the  H2S  undissociated,  and  ignore 
these  corrections,  which  would  probably  reduce,  rather  than  increase,  the 
quantity  of  hydrogen  which  might  result  from  pyrite. 

If  the  iron  had  all  been  locked  up  in  the  mineral  chalcopyrite  (CuFeS2) 
the  hydrogen  might  be  accounted  for,  but  chemical  tests  failed  to  detect 
the  copper  which  this  supposition  would  require.  Just  how  much  hydrogen 
might  be  expected  from  iron  nitride  (Fe2N)  is  not  certain,  since,  in  the 
presence  of  superheated  steam,  the  nitrogen  is  more  likely  to  unite  with 
hydrogen  and  come  off  as  ammonia  rather  than  as  free  nitrogen,  and 
ammonia  is  not  dissociated  short  of  the  electric  spark.  That  most  of  the 
iron  in  the  quartz  is  in  the  form  of  a  nitride  is  highly  improbable.  Iron 
carbide  also  would  not  yield  sufficient  hydrogen. 

Another  mineral  apparently  containing  very  little  iron,  but  which 
yielded  considerable  hydrogen,  was  the  beryl  of  analyses  101  and  lOla. 


48  THE    GASES   IN   BOCKS. 

Though  as  transparent  as  window-glass,  one  volume  of  this  beryl  con- 
tributed 0.31  volume  of  hydrogen.  A  determination  of  its  accessible  iron 
was  made  by  pursuing  the  same  method  as  was  used  for  the  quartz.  The 
results  were: 

35.00  gms.  beryl  contained 0.0003    gm.  Fe2O3 

127.52  gms.  beryl  would  contain 00109  gm.  Fe2O3 

127.52  gms.  beryl  would  contain 00076  gm.  Fe 

Fe  (as  FeO)  required  to  give  1  c.c.  hydrogen 00748  gm. 

Maximum  amount  hydrogen  from  reaction 0.10  c.c. 

Hydrogen  actually  obtained  (0°  and  760  mm.) 14.89  c.c. 

Hydrogen  not  from  this  reaction 14.79  c.c. 

This  beryl  expelled  nearly  150  times  as  much  hydrogen  as  can  be 
assigned  to  the  interaction  of  steam  and  ferrous  oxide  under  the  most 
generous  assumptions.  The  actual  hydrogen  is  37  times  the  maximum 
quantity  possible  from  this  weight  of  iron,  either  as  pyrite  or  in  the  metallic 
state.  Here  is  a  very  declared  case  demonstrating  the  inadequacy  of  chem- 
ical reactions  involving  iron  to  generate  the  hydrogen  obtained. 

Heated  in  a  closed  tube  with  a  limited  amount  of  air,  beryl  is  known 
to  give  up  a  small  quantity  of  water  which,  in  some  varieties  of  the  mineral, 
may  reach  2  per  cent.  The  question  whether  the  excess  of  hydrogen  over 
that  possible  from  reactions  between  water  and  iron  could  have  arisen 
from  the  dissociation  of  this  water  is  easily  answered.  The  recent  researches 
of  Nernst  upon  the  dissociation  of  steam  indicate  that,  at  temperatures 
below  2000°  C.,  the  process  takes  place  only  to  a  very  limited  extent. 
At  1124°  C.,  which  is  somewhat  above  the  point  to  which  the  beryl  was 
heated,  only  0.0078  per  cent  of  the  total  steam  can  be  dissociated.1  At 
this  temperature,  127  grams  of  beryl  containing  2  per  cent  of  water  should, 
on  the  basis  of  Nernst's  figures,  yield  0.24  cubic  centimeter  of  hydrogen, 
provided  the  gas  was  quickly  cooled.  Hence  only  a  small  portion  of  the 
hydrogen  can  be  attributed  to  the  dissociation  of  water  present  in  the 
mineral. 

To  the  question  of  the  importance  of  ferrous  salts  in  the  production  of 
hydrogen,  it  is  possible  that  meteorites,  which  have  usually  been  regarded 
as  free  from  water,  can  add  testimony  of  some  value.  Though  it  is  true 
that  in  freshly  fallen  specimens  hydrous  minerals  have  not  yet  been  recog- 
nized,2 nevertheless,  the  researches  of  Graham,  Mallet,  Wright,  and  Dewar, 
besides  my  analyses  of  the  Allegan,  Estacado,  and  Toluca  meteorites, 
have  shown  that  these  bodies,  when  heated,  give  off  much  gas,  rich  in 
hydrogen.  If  these  meteorites  really  contained  no  water,  either  original 
or  by  absorption  from  the  earth's  atmosphere,  the  hydrogen  obtained 
from  them  can  not  be  attributed  to  the  decomposition  of  water;  it  must 
have  been  held  within  the  mass  of  each  meteorite,  either  entrapped  or 
occluded.3  But  in  several  instances,  at  least,  the  investigators  have  stated 
that  a  certain  quantity  of  water  was  driven  off,  though  perhaps  this  came 
from  weathered  aerolites.  The  chemical  analysis  of  the  Allegan  meteorite, 

1  Nernst,  Chem.  Central-Blatt,  1905,  2,  p.  290. 

7  Farrington,  Jour,  of  Geol.,  vol.  9  (1901),  p.  532. 

3  It  is  to  be  remembered  that  a  few  meteorites  have  been  found  to  contain  hydro- 
carbons, from  which  hydrogen  might  arise,  but  the  presence  of  these  hydrocarbons  from 
inorganic  sources  is  more  remarkable  than  that  of  hydrogen  itself. 


STATES    OF   THE    GASES.  49 

which  was  dug  up  while  still  hot,  gave  Stokes  0.25  per  cent  of  water.1 
Perhaps  this  was  moisture  absorbed  from  the  air  by  deliquescent  com- 
pounds, such  as  lawrencite;  still,  on  the  other  hand,  there  appears  no 
reason,  at  the  present  time,  why  a  part  of  this  water  should  not  be  a  pri- 
mary constituent  of  the  meteorite.  This  uncertainty  points  out  the  desir- 
ability of  further,  and  more  critical,  studies  upon  the  composition  and 
properties  of  meteorites,  before  attempting  to  base  an  argument  upon  the 
absence  of  water  in  these  bodies. 

Other  possible  sources  of  hydrogen  are  hydrogen  sulphide,  hydro- 
carbons, and  the  products  of  radioactivity.  As  the  decomposition  of 
sulphureted  hydrogen  has  already  been  mentioned,  and  is  also  treated 
under  the  head  of  that  gas,  it  need  not  be  discussed  here.  Hydrocarbons 
can  only  be  represented  in  small  quantities  in  igneous  rocks,  and  should 
produce  more  methane  than  free  hydrogen.  Unless  the  analysis  shows 
much  marsh-gas,  hydrogen  from  this  source  must  be  unimportant. 

CARBON    DIOXIDE. 

The  carbonates  of  most  metals  are  decomposed  by  heat  with  the  liber- 
ation of  carbon  dioxide.  On  this  account  the  determination  of  the  carbon 
dioxide  yielded  by  rocks  which  have  undergone  much  carbonation  is  of 
little  value.  Many  rocks  which  appear  to  be  perfectly  fresh  have  neverthe- 
less suffered  slight  carbonation  while  in  the  zone  of  weathering,  and  thus 
possess  carbon  dioxide  in  a  combined  state  ready  to  be  evolved  when  suffi- 
ciently heated.  This  carbon  dioxide  from  the  non-gaseous  constituents 
of  the  rock  embarrasses  the  determination  of  the  free  gas,  since  there  is  no 
way  of  separating  the  carbonic  acid  from  these  different  sources. 

The  degree  of  heat  necessary  to  decompose  carbonates  throws  some 
light  on  the  question.  Erdmann  and  Marchand  state  that  already  at 
400°  traces  of  carbon  dioxide  are  given  off  from  calcium  carbonate.2  The 
studies  of  Debray  show  that  at  the  boiling-points  of  mercury  and  sulphur, 
350°  and  448°  respectively,  the  development  of  CO2  from  calcite  in  vacuo 
is  inappreciable.3  The  same  investigator  found  that  at  860°  calcite  gives 
up  carbonic  anhydride  until  a  pressure  of  85  millimeters  is  reached,  when  the 
action  ceases.  At  1040°  the  pressure  may  rise  to  520  millimeters  before 
the  evolution  of  gas  is  stopped.  In  the  presence  of  carbon  dioxide  at  the 
ordinary  atmospheric  pressure,  calcite  retains  all  of  its  optical  and  other 
properties  unaltered,  even  at  1040°.  Carbon  dioxide  from  calcium  carbonate 
is  thus  not  of  any  quantitative  importance  below  450°.  In  general,  most 
of  the  carbonic  acid  from  the  rocks  is  expelled  at  temperatures  above 
450°.  But  considerable  C02  often  appears  before  the  heat  reaches  400°, 
as  is  shown  by  the  Baltimore  gneiss.  Perhaps  this  gas  may  be  assigned  to 
ferrous  carbonate.  Iron  carbonate  would  be  expected  to  decompose  more 
readily  than  calcium  carbonate,  though  I  have  been  unable  to  discover  at 
what  temperature  the  process  commences. 

1  Ante,  p.  21. 

*  Erdmann  and  Marchand,  cited  by  Gmelin-Kraut,  Anorg.  Chem.,  2,  p.  354. 

3  Debray,  Comptes  Rendus,  vol.  64,  p.  603. 


50 


THE    GASES    IN    ROCKS. 


When  a  finely  powdered  igneous  rock  is  treated  with  hydrochloric 
acid  and  gently  warmed,  a  few  small  bubbles  of  carbon  dioxide  usually 
are  seen  to  rise  to  the  surface  of  the  acid.  This  gas  comes  from  the  action 
of  the  acid  upon  small  quantities  of  carbonate  present  in  the  rock.  To 
test  the  quantitative  importance  of  this  action  and  to  discover  whether 
other  gases  are  freed  by  acid,  25.13  grams  of  diabase  from  Nahant,  Massa- 
chusetts,1 were  placed  in  a  flask  connected  with  the  mercury-pump,  and  the 
air  removed.  Dilute  sulphuric  acid  was  introduced  into  the  flask  through 
a  dropping  funnel.  The  gas  developed  in  the  cold  during  the  first  1\  hours 
was  found  to  have  the  following  composition: 

TABLE  35. 


Per  cent. 

Volumes. 

Hydrogen  sulphide  
Carbon  dioxide  

0.00 
98.10 

644 

Methane  

03 

00 

Hydrogen 

25 

02 

Nitrogen 

162 

10 

Total  

100.00 

6.56 

Practically  all  of  the  carbon  dioxide  thus  set  free  is  to  be  assigned  to 
a  carbonate. 

The  apparatus  was  allowed  to  stand  for  three  days,  during  which  time 
more  gas  came  off.  At  the  end  of  this  period,  the  powder  was  washed, 
dried,  and  then  submitted  to  the  ordinary  process  of  heating  in  the  tube. 
Of  the  gas  received,  38.19  per  cent,  or  0.62  volume  per  volume  of  rock, 
was  carbon  dioxide.  Powder  from  the  same  specimen  of  diabase,  not 
treated  with  acid,  yielded  8.51  volumes  of  carbonic  anhydride  in  the  com- 
bustion-tube. This  amounted  to  61.25  per  cent  of  the  total  gas.2 

While  carbon  dioxide,  both  gaseous  and  liquid,  occurs  in  minute  cavities 
in  certain  minerals  and  rocks,  and  while  rocks  also,  doubtless,  contain 
some  of  this  gas  in  a  state  of  occlusion,  it  seems  probable,  on  account  of 
the  wide  dissemination  of  carbonates  in  small  quantities  through  the 
accessible  rocks  near  the  earth's  surface,  that  the  greater  part  of  the  carbon 
dioxide  obtained  by  the  method  of  heating  rock  material  in  vacuo  is  derived 
from  the  decomposition  of  carbonates  in  the  combustion-tube.  It  may 
be  assumed  that  more  of  the  carbonates  in  igneous  rocks  are  secondary 
than  primary.  But  though  a  knowledge  of  this  immediate  source  of  much 
of  the  carbon  dioxide  in  the  rocks  does  not  lead  far  toward  the  elucidation 
of  the  problem  of  the  ultimate  source  of  this  gas,  it  imposes  no  restrictions 
upon  the  more  comprehensive  view  that  the  carbonic  acid  which  is  now 
locked  up  in  the  rocks  chemically,  as  a  result  of  weathering  and  carbona- 
tion,  was  given  to  the  atmosphere  and  hydrosphere  originally  from  the 
magmas  themselves. 

CARBON   MONOXIDE. 

Metallic  iron  and  ferrous  salts  reduce  carbon  dioxide  to  monoxide 
under  practically  the  same  conditions  that  they  liberate  hydrogen  from 
water-vapor. 


Analysis  No.  88. 


J  Analysis  No.  86. 


STATES   OF   THE    GASES.  51 

3FeO  +  CO2  =  Fe3O4  +  CO 

While  this  action  commences  below  400°,  it  takes  place  slowly,  and  it  is 
chiefly  at  higher  temperatures  that  it  becomes  of  quantitative  importance. 
As  in  the  case  of  hydrogen  and  water-vapor,  this  reaction  is  reversible, 
the  direction  in  which  it  will  proceed  depending  upon  the  proportions  of 
the  substances  present.  Either  metallic  iron  or  ferric  oxide,  heated  in  a 
mixture  of  equal  parts  of  carbon  monoxide  and  carbon  dioxide,  produces 
ferrous  oxide.1  Siderite  at  red  heat  passes  into  a  magnetic  oxide  with  the 
formation  of  both  carbonic  acid  and  carbonic  oxide.  According  to 
Dobereiner  this  reaction  takes  place  as  follows:2 

5FeCO3  =  3FeO.Fe2O3  +  4CO2  +  CO 

Glasson,2  however,  says  that  4FeO.Fe2O3  results,  at  first  giving  two  parts 
of  CO2  and  one  of  CO,  but  that  later  the  proportion  changes  to  five  parts 
of  CO2  and  one  of  CO. 

It  is,  therefore,  the  normal  thing  for  a  rock  containing  carbon  dioxide 
(whether  occluded,  or  in  cavities,  or  a  carbonate)  and  iron  in  the  ferrous 
condition  to  generate  carbon  monoxide  on  the  application  of  heat.  In 
this  connection  it  may  be  noted  that  carbon  monoxide  rises  very  conspic- 
uously in  relative  importance  whenever  there  is  metallic  iron  present  in 
the  material  tested.  The  iron-bearing  basalt  of  Ovifak,  Greenland,  gave 
21.63  per  cent  of  this  gas  compared  with  46.50  per  cent  of  the  dioxide;8 
the  Allegan  meteorite,  38.61  per  cent  of  CO  and  41.74  per  cent  of  CO2;4 
while  the  Estacado  meteorite  developed  29.31  per  cent  monoxide  and  only 
28.47  per  cent  dioxide.5  These  were  specimens  of  stony  material  contain- 
ing grains  of  metallic  iron.  Quite  different  is  the  Toluca  iron  meteorite, 
whose  nearly  pure  metal  evolved  71.05  per  cent  carbonic  oxide  with  but 
6.40  per  cent  carbonic  anhydride.6  Wright's  figures  for  iron  meteorites 
are  equally  noted  for  high  percentages  of  carbon  monoxide.7 

However,  there  are  two  other  chemical  sources  for  carbon  monoxide, 
one  of  which  is,  perhaps,  especially  applicable  to  iron  meteorites.  It  is 
known  that  the  carbides  of  chromium  and  iron,  when  heated  with  the 
oxides  of  these  metals,  produce  carbonic  oxide.8  As  these  meteorites  often 
contain  considerable  carbon,  some  of  it  perhaps  as  a  carbide,  scrupulous 
care  is  always  necessary  in  preparing  the  metal  for  the  analysis,  to  avoid 
introducing  any  rust  from  the  oxidized  exterior  of  the  mass. 

The  other  principle  must  always  be  operative  in  the  combustion-tube. 
Boudouard  has  shown  that  at  the  temperatures  of  the  combustion-furnace 
hydrogen  reduces  carbon  dioxide,  forming  carbon  monoxide  at  the  expense 
of  both  hydrogen  and  the  dioxide.9 

1  Wright  and  Luff,  Jour.  Chem.  Soc.,  vol.  33  (1878),  p.  504. 

2  Cited  by  Gmelin-Kraut,  Anorg.  Chem.,  vol.  3,  p.  319. 

3  Analysis  No.  45. 

*  Analysis  No.  106. 

*  Analysis  No.  107. 

*  Analysis  No.  108. 

7  See  p.  6. 

8  Borchers  and  McMillan,  Electric  Smelting  and  Refining,  p.  545. 

9  O.  Boudouard,  Chem.  Central-Blatt  (1901),  1,  p.  1350. 


52  THE    GASES   IN    ROCKS. 


Equal  volumes  of  hydrogen  and  carbon  dioxide  heated  at  850°  for 
one  hour  gave  CO2  44.3  per  cent,  CO  8.3,  H2  42.0,  and  H2O  5.4  per  cent. 
Heated  for  three  hours  under  the  same  conditions,  the  proportion  of  carbon 
monoxide  rose  to  18  per  cent.  When  rocks  are  heated  for  analysis,  the 
gas  is  usually  pumped  off  at  short  intervals,  and  this  reaction,  because  of 
its  slowness,  becomes  less  important.  Htittner  has  appealed  to  this  reaction 
to  explain  the  presence  of  carbon  monoxide  in  minerals. 

But  metallic  iron  also  has  a  penchant  for  absorbing  carbon  monoxide 
at  the  proper  temperature.  This  process  is  usually  called  occlusion,  and 
may  perhaps  partake  of  the  nature  of  a  combination  in  which  the  gas 
temporarily  unites  with  the  iron  as  iron  carbonyl,  Fe(CO)4,x  an  unstable 
compound  readily  giving  up  carbonic  oxide.  It  seems  likely  that  a  portion 
of  the  carbon  monoxide  developed  from  these  irons,  particularly  those  of 
meteoritic  origin,  actually  exists  in  the  iron  as  monoxide,  and  that  not  all 
of  it  has  been  formed  by  reduction  of  the  dioxide. 

SULPHUR   DIOXIDE. 

Certain  rocks,  when  heated,  disengaged  sulphur  dioxide  in  considerable 
quantities.2  These  were  ferruginous  rocks  of  rusty  appearance,  generally 
metamorphosed  pyritiferous  shales  which  had  undergone  much  weather- 
ing. By  oxidation,  the  original  pyrite  had  been  partially  converted  into 
ferrous  sulphate  (FeSO4)  and  basic  ferric  sulphate  (Fe2S2O9),  both  of  which 
were  decomposed  by  the  heat  of  the  combustion-furnace. 

2FeS04  =  Fe2O3  +  S02  +  S03         Fe2S2O9  =  Fe2O3  +  2SO3 

The  sulphur  trioxide  was  reduced  to  the  dioxide  either  by  hydrogen  sul- 
phide, hydrogen,  ferrous  oxide,  or  sulphur. 


It  has  been  my  observation  that  whenever  sulphur  dioxide  was  evolved 
a  slight  sublimate  of  sulphur  collected  toward  the  cool  end  of  the  tube. 
This  may  have  been  derived  from  the  reaction  above,  or  from  hydrogen 
sulphide  and  sulphur  dioxide,  coming  from  ferrous  disulphide  and  sulphate, 
respectively,  and  which  can  not  exist  together. 


The  sulphur  dioxide  obtained  in  the  study  of  rocks  is  all  assigned  to 
these  reactions,  though  it  is  not  impossible  that  this  compound  may  occur 
in  small  quantities,  as  a  gas  or  a  liquid,  imprisoned  in  minute  cavities. 

HYDROGEN    SULPHIDE. 

When  iron  pyrites  (FeS2)  is  heated  in  a  stream  of  hydrogen,  ferrous 
sulphide  (FeS)  and  free  sulphur  result.3  Though  no  hydrogen  sulphide 

1  Fe  and  CO  also  exist  feebly  united  in  other  proportions,  as  iron  pentacarbonyl, 
Fe(CO)5,  and  heptacarbonyl,  Fe(CO)7. 

2  Analyses  Nos.  43,  65,  93,  and  109. 

3  Rose,  Pogg.  Ann.,  vol.  5,  p.  533. 


STATES    OF   THE    GASES.  53 

is  formed  in  this  manner,  that  gas  is  produced  when  pyrite  is  decomposed 
by  steam  at  high  temperatures.1 

FeS2  +  H20  =  FeO  +  H2S  +  S 

As  pyrite  is  frequently  present  in  igneous  rocks  which  generally  evolve 
water-  vapor  upon  the  application  of  heat,  the  limited  quantities  of  hydro- 
gen sulphide  obtained  may  be  explained  in  this  way.  But  unless  the 
hydrogen  sulphide  be  removed,  this  process  can  proceed  only  to  a  certain 
point,  for,  according  to  Berzelius,  iron  disulphide  is  formed  when  FeCO3, 
Fe3O4,  Fe2O3,  or  Fe(OH)3  is  heated  with  hydrogen  sulphide  to  temperatures 
between  100°  and  red  heat.2  At  red  heat,  a  current  of  dry  hydrogen  sul- 
phide completely  converts  Fe3O4  into  Fe3S4  in  two  hours,  while  a  still 
further  increase  of  temperature  results  in  the  formation  of  FeS  and  a  deposit 
of  sulphur.3 

An  inspection  of  the  analyses  shows  that  sulphureted  hydrogen  is 
rarely  obtained  in  large  amounts  from  igneous  rocks.  An  average  of  75 
analyses  from  a  wide  range  of  rocks  (but  omitting  bituminous  shales) 
gave  0.59  per  cent  of  this  gas.  But  this  figure  is  not  a  good  working  aver- 
age, since  it  has  been  much  influenced  by  the  high  sulphide  percentage 
of  a  few  individuals.  Deducting  the  five  highest  of  these,  the  remaining 
70  analyses  give  an  average  of  0.27  per  cent  of  hydrogen  sulphide.  In  19 
cases  out  of  the  75,  this  gas  was  entirely  lacking. 

While  it  is  probable  that  not  much  of  this  gas  was  given  off  from  the 
rock  material  in  the  first  place,  a  portion  of  it  doubtless  disappeared  before 
passing  through  the  pump  into  the  gas-receiver.  At  the  temperature  of 
the  combustion-furnace,  hydrogen  sulphide  is  apt  to  be  partially  dissociated 
into  its  elements,  thus  swelling  the  already  large  volume  of  hydrogen  pres- 
ent.4 Gautier  states  that  sulphur  heated  in  a  tube  filled  with  hydrogen 
sulphide  causes  the  decomposition  of  the  gas  with  the  result  that  its  sul- 
phur is  added  to  the  free  sulphur,  while  hydrogen,  nearly  pure,  remains.5 
When  the  rock  has  been  considerably  weathered,  and  some  of  the  pyrite 
oxidized  into  iron  sulphate,  so  that,  in  addition  to  hydrogen  sulphide, 
sulphur  dioxide  is  disengaged,  the  former  gas  will  be  partially  or  com- 
pletely decomposed,  depending  upon  the  relative  proportions  of  the  two 
gases. 


The  bituminous  shale  from  Newsom's  Station,  near  Nashville,  Ten- 
nessee,6 yielded  sulphureted  hydrogen  to  the  extent  of  30.94  per  cent  of 
the  total  gas,  which  is  equivalent  to  the  unusual  amount  of  29.38  volumes 
of  hydrogen  sulphide  from  one  volume  of  shale.  A  specimen  of  the  well- 

1  With  an  excess  of  steam  the  reaction  goes  further:   3FeS2  +  4H2O  = 
+  3S+H2. 


2  Berzelius,  cited  by  Graham-Otto,  Anorg.  Chem.,  4,  p.  718. 

3  Sidot,  Chem.  Central-Blatt,  vol.  40  (1869),  p.  1038. 


!  See'  p.  47. 

6  Gautier,  Comptes  Rendus,  vol.  132  (1901),  p.  189.  When  pyrite  is  heated  either 
in  a  vacuum,  or  in  a  stream  of  dry  carbon  dioxide,  Fe7S8  and  free  sulphur  result  (Berzelius, 
Rammelsberg.  cited  in  Gmelin-Kraut,  Anorg.  Chem.,  3,  p.  335). 

"Analysis  No.  41. 


54  THE    GASES   IN    ROCKS. 

known  "oil  rock"  from  a  lead  and  zinc  mine  near  Platteville,  Wisconsin, 
produced  6.79  per  cent  hydrogen  sulphide,  corresponding  to  3.90  volumes 
per  volume  of  rock.1  How  prolific  a  source  of  hydrogen  sulphide  the  organic 
matter  in  certain  shales  may  be,  is  indicated  by  these  two  experiments. 
If  a  shale  of  this  sort,  undergoing  extensive  metamorphism,  did  not  lose 
all  of  its  sulphur  compounds  during  the  transforming  process,  the  meta- 
morphic  product  might  still  be  distinguished  by  a  high  content  of  hydrogen 
sulphide.  Perhaps  the  specimen  of  Baltimore  gneiss  obtained  from  Spring 
Mill,  on  the  Schuylkill  River,2  from  which  4.91  per  cent,  or  0.30  volume, 
of  sulphureted  hydrogen  was  extracted,  may  have  been  derived  from  such 
a  shale.  Other  sulphur  compounds  in  small  amounts  have  been  noted 
in  the  gases  from  rocks.  The  potassium  hydroxide  solution  in  the  Lunge 
nitrometer,  after  having  absorbed  whatever  hydrogen  sulphide  and  carbon 
dioxide  there  may  have  been  in  the  gas  under  analysis,  frequently  emits 
an  odor  suggesting  a  mercaptan.  When  air  is  let  into  the  pump  and  tubes, 
after  the  removal  of  the  gas  for  analysis,  and  then  pumped  out,  it  usually 
is  charged  with  odors  of  more  or  less  offensive  nature.  These  suggest 
that  other  complex  reactions  prevail  at  the  high  temperatures  employed 
in  extracting  the  gas.  Gautier  detected  a  trace  of  ammonium  sulphocyanide 
in  the  gas  from  a  granitoid  porphyry  from  Esterel.3 

METHANE. 

Moissan  believed  that  the  hydrocarbons  of  the  petroleum  type  which 
occur  in  the  earth's  crust  were,  in  many  cases,  derived  from  the  action  of 
water  upon  metallic  carbides  in  the  deep  interior.4  His  important  researches 
upon  carbides  form  the  experimental  basis  for  the  hypothesis  that  the 
methane  obtained  by  heating  igneous  rocks  has  resulted  from  these  com- 
pounds. Even  with  cold  water,  the  carbides  of  barium,  strontium,  calcium, 
and  lithium  give  pure  acetylene,  while  under  the  same  conditions  aluminum 
and  beryllium  carbides  generate  pure  methane. 

CaC2 + 2H2O  =  Ca(OH)2 + C2H2  A14C3  +  12H20  =  4A1(OH)3  +  3CH4 

The  carbides  of  the  rarer  metals,  cerium,  lanthanum,  yttrium,  and 
thorium,  yield  various  mixtures  of  acetylene  and  marsh-gas;  from  manga- 
nese carbide,  marsh-gas  and  hydrogen  result.  But  the  most  remarkable 
of  the  carbides  is  that  of  uranium,  which  with  water  at  ordinary  tempera- 
tures produces  (in  addition  to  a  gaseous  mixture  of  methane,  hydrogen, 
and  ethylene)  both  liquid  and  solid  hydrocarbons.  Under  ordinary  condi- 
tions water  does  not  decompose  the  carbides  of  molybdenum,  tungsten, 
chromium,  or  iron. 

These  reactions  suggest  two  alternative  hypotheses  to  explain  the 
occurrence  of  methane  in  the  gas  obtained  from  igneous  rocks.  The  most 
limited  of  these  supposes  the  marsh-gas  to  be  produced  from  a  carbide 

1  Analysis  No.  42. 

1  Analysis  No.  28. 

s  Gautier,  Comptes  Rendus,  vol.  132,  pp.  61-62. 

4  Moissan,  Proc.  Roy.  Soc.,  vol.  60  (1897),  pp.  156-160. 


STATES   OF   THE    GASES.  55 

in  the  combustion-tube.  Such  a  carbide  must  have  withstood  the  action 
of  water,  both  magmatic  and  meteoric,  ever  since  the  solidification  of  the 
rock.  The  other  hypothesis  seeks  to  avoid  this  difficulty  by  postulating 
carbides  in  the  very  hot  rocks  where  the  hydrogen  and  oxygen  may  not  be 
combined  as  water;  then,  at  a  later  stage,  it  allows  water  to  decompose 
the  carbides  with  the  evolution  of  marsh-gas,  which  is  retained  within  the 
rock.  In  this  case  the  gas  itself  would  exist  in  the  rock  specimen  tested. 

It  is  to  be  noted  that  several  of  these  carbides,  including  that  of  the 
widespread  element  calcium  and  the  less  stable  sodium  and  potassium 
compounds,1  give  acetylene  when  decomposed  by  water.  In  none  of  the 
rocks  examined,  with  one  exception,  has  acetylene  been  detected.  This 
may  possibly  eliminate  calcium  carbide  from  the  gas-contributing  com- 
pounds in  the  rocks.  The  absence  of  acetylene  also  carries  with  it  some 
slight  evidence  against  carbides  in  general,  since  calcium  plays  a  very 
important  role  in  rock  evolution,  and  it  is  not  likely  that  acetylene,  if 
formed,  would  pass  into  methane.  However,  it  is  not  impossible  that 
aluminum  carbide,  which  yields  methane  with  water,  may  exist  in  the 
earth's  crust  while  calcium  carbide  is  lacking.  According  to  F.  W.  Clarke,2 
aluminum  constitutes  8.16  per  cent  of  the  solid  crust  of  the  earth,  while 
iron  and  calcium  comprise  4.64  and  3.50  per  cent,  respectively.  Aluminum 
also  forms  very  stable  compounds  in  nature.  Moreover,  aluminum  oxide 
fused  in  the  electric  furnace  with  calcium  carbide  gives  yellow  crystals  of 
aluminum  carbide.3  Perhaps  at  high  temperatures  iron  carbide  might 
be  decomposed  by  steam  with  the  formation  of  marsh-gas. 

Besides  carbides,  organic  matter  suggests  itself  as  a  possible  source  of 
the  methane.  This  organic  matter  may  have  been  either  (1)  accidentally 
introduced  into  the  combustion-tube,  or  (2)  have  been  incorporated  in  the 
rocks  from  life  which  inhabited  the  earth  during  the  later  stages  of  growth, 
as  outlined  by  the  planetesimal  hypothesis.  The  first  possibility  may  be 
practically  dismissed,  since  great  care  was  exercised  to  avoid  the  intro- 
duction of  any  foreign  matter  with  the  rock  powder.  If  dependent  upon 
such  accidental  conditions,  this  gas  would  only  occasionally  be  present. 
Under  the  planetesimal  hypothesis,  life  may  have  existed  long  before  the 
growth  of  the  planet  was  completed  and  its  present  size  attained.  Organic 
deposits  buried  in  sedimentary  beds  which  have  since  undergone  exten- 
sive metamorphism  should  furnish  marsh-gas.  These  rocks,  worked  over 
and  reworked  by  the  volcanic  activity  in  Archean  times,  might  perhaps 
account  for  the  widespread  occurrence  of  this  gas.  Formed  in  this  way, 
it  may  be  retained  in  the  rocks  as  a  free  or  occluded  gas,  since  it  is  very 
stable  at  high  temperatures. 

Other  theoretical  sources  of  methane  are  high- temperature  reactions 
within  the  combustion-tube,  in  which  hydrogen  and  the  oxides  of  carbon 
participate.  Brodie  produced  6  per  cent  of  marsh-gas  by  submitting 

1  Moissan,  Jour.  Chem.  Soc.,  vol.  64,  2,  p.  332. 
1  F.  W.  Clarke,  Bull.  168  U.  S.  G.  S.  (1900),  p.  15. 

3  Moissan,  Comptes  Rendus,  125  (1897),  pp.  839-844;   Jour.   Chem.  Soc.,  vol.  64 
(1898),  2,  p.  161. 


56  THE    GASES    IN   ROCKS. 

approximately  equal  volumes  of  hydrogen  and  carbon  monoxide  to  the 
action  of  electricity  for  five  hours  in  an  induction-tube.1  From  his  results 
he  expressed  this  reaction  by  the  equation, 


Though  it  is  not  safe  to  assume  that  this  reaction  will  take  place  at 
the  temperatures  of  the  combustion-furnace,  the  observation  that  marsh-gas 
is  obtained  when  a  rock  powder,  exhausted  of  its  gases,  is  exposed  to  the 
air  for  a  few  months,  and  reheated,  possibly  points  toward  some  reaction 
of  this  nature. 

NITROGEN. 

If  the  nitrogen  which  is  obtained  from  heating  igneous  rock  powders 
in  vacuo  is  derived  from  some  chemical  compounds  decomposable  at  red 
heat,  a  metallic  nitride  at  once  suggests  itself  as  the  most  probable  form  in 
which  the  nitrogen  would  occur.  Iron  nitride  may  be  taken  as  the  type  for 
discussion.  While  different  nitrides  of  iron,  having  the  compositions  of 
Fe2N2,  Fe2N,  and  Fe5N2,  have  been  described  by  some  authors,  a  compre- 
hensive study,  by  Fowler,  of  this  formerly  little-known  compound,  forces 
the  conclusion  that  there  exists2  only  one  iron  nitride,  Fe2N.  This  com- 
pound may  be  prepared  by  the  action  of  ammonia  either  upon  ferrous 
chloride,  or  finely  divided  iron.  While  the  action  between  ferrous  chloride 
and  ammonia  commences  near  the  melting-point  of  lead  (327°),  a  tem- 
perature of  600°  appears  to  be  necessary  for  the  production  of  iron  nitride 
in  quantity.3  The  nitride  can  also  be  produced  at  850°  to  900°,  but  this 
is  probably  the  highest  limit  of  the  reaction.4 

This  nitride  is  very  soluble  in  dilute  acids,  giving  ammonia.  When 
heated  to  redness  in  hydrogen,  ammonia  results.  At  200°  it  is  oxidized 
in  the  air  to  ferric  oxide,  abandoning  nitrogen,  which  does  not  appear  to 
be  oxidized.  At  100°  steam  causes  a  slight  evolution  of  ammonia.  Accord- 
ing to  Fowler  the  temperature  of  decomposition  of  iron  nitride  in  an  inert 
gas  (nitrogen)  must  certainly  be  above  600°. 

Silvestri  has  found  iron  nitride  coating  some  of  the  fumarole  deposits 
of  Etna,5  and  Boussingault  6  recognized  nitrogen  in  the  Lenarto  meteor- 
ite by  certain  tests  which  led  him  to  believe  that  it  existed  there  as  a 
metallic  nitride.  Silvestri  discovered  that  at  red  heat  the  nitride  from 
Etna  was  decomposed,  delivering  up  its  nitrogen.  His  experiments  show- 
ing that  iron  nitride  may  be  prepared  artificially,  by  igniting  the  ordinary 
lava  in  a  current  of  ammonium  chloride  vapor,  probably  illustrate  what 
takes  place  in  the  fumaroles.  But  this  nitride,  which  derives  its  nitrogen 
from  ammonia  or  ammonium  salts,  in  no  way  requires  the  existence  of 
nitrides  within  the  magma  itself,  except  as  a  possible  source  for  the  nitro- 
gen which  unites  with  hydrogen  to  form  the  ammonia.  There  is  danger 
in  transferring  the  characteristics  of  fumarole  deposits,  which  are  formed 

1  Sir  B.  C.  Brodie,  Proc.  Roy.  Soc.,  vol.  21  (1873),  p.  245. 
1  Fowler,  Jour.  Chem.  Soc.,  vol.  79  (1901),  pp.  285-299. 
8  Fowler,  Chem.  News,  vol.  82  (1900),  p.  245. 

4  Beilby  and  Henderson,  Jour.  Chem.  Soc.,  vol.  79,  p.  1245. 

5  Silvestri,  Pogg.  Ann.,  vol.  157  (1876),  pp.  165-172. 

8  Boussingault,  Comptes  Rend  us,  vol.  53  (1861),  pp.  78-79. 


STATES    OF   THE    GASES.  57 

in  limited  quantities  under  the  quite  exceptional  conditions  of  abundant 
currents  of  free  gases  and  very  active  hot  vapors,  to  the  main  magmas. 

If  the  nitrogen  obtained  from  rock  powders  be  derived  from  a  nitride, 
it  should  be  accompanied  by  ammonia,  since,  in  the  presence  of  hydrogen 
or  water-vapor,  it  is  this  gas,  rather  than  free  nitrogen,  which  is  given  off. 
Tests  made  with  Nessler's  solution  show  that  ammonia  is  one  of  the  gases 
extracted  from  rocks,  though  always  appearing  in  limited  amounts.  In 
the  process  ordinarily  employed  for  extracting  the  gas,  it  is  absorbed  by 
the  calcium  chloride  drying-tube.  Ammonia  is  scarcely  to  be  considered 
as  a  source  of  free  nitrogen,  since  this  compound  is  only  dissociated  at  the 
temperature  of  the  electric  spark. 

Whether  all  of  the  free  nitrogen  can  be  assigned  to  the  decomposition 
of  iron  nitride  may  be  tested  with  the  quartz  from  New  South  Wales.1  Sup- 
posing all  of  the  iron  in  this  quartz  to  have  existed  as  iron  nitride,  and 
to  have  been  completely  decomposed  without  the  production  of  any  am- 
monia, the  analysis  still  shows  an  excess  of  nitrogen  over  what  could  have 
been  produced  in  this  way.  The  reaction  may  be  taken  as 


102.72  gms.  quartz  contained  ............................  0.0058  gm.  Fe 

Fe  (as  Fe2N)  required  to  give  1  c.c.  nitrogen  ................  0100  gm. 

Nitrogen  possible  from  reaction  ...........................  68  c.c. 

Nitrogen  actually  obtained  (0°  and  760  mm.)  ...............  86  c.c. 

Excess  of  nitrogen  .......................................  28  c.c. 

A  duplicate  determination  of  the  iron  in  this  weight  of  quartz  gave  only 
0.0048  gram;  on  this  basis,  the  excess  of  nitrogen  would  be  still  greater. 
It  is  highly  improbable  that  all  of  the  iron  in  this  quartz  was  combined  as 
a  nitride.  Some  of  it  was  unquestionably  pyrite.  To  ascertain  how  much 
of  this  nitrogen  can  be  ascribed  to  atmospheric  air  adhering  to  the  tubes, 
as  well  as  to  leakage  during  the  process  of  extraction,  a  blank  combustion 
was  resorted  to.  The  empty  combustion-tube  was  kept  at  bright-yellow 
heat  for  the  length  of  time  which  was  required  to  expel  the  gas  from  the 
quartz.  0.15  cubic  centimeter  of  gas  was  collected  in  the  receiver  when 
the  tube  was  exhausted  by  the  pump.  Adhesion  of  air  to  the  quartz  itself 
might  be  supposed  to  increase  this  figure,  though  the  material  used  for  this 
analysis  was  not  the  usual  fine  powder,  but  small  fragments  which  would 
be  less  liable  to  entrap  air.  In  general,  while  iron  nitride  is  to  be  accepted 
as  a  possible  source  of  this  nitrogen,  it  is  inadequate  to  produce  the  quanti- 
ties of  this  gas  determined  by  analysis.  The  presence  of  other  metallic 
nitrides  in  this  comparatively  pure  quartz  does  not  seem  likely.  Silicon 
nitride,  however,  may  be  present  and  might  possibly  contribute  a  portion 
of  the  nitrogen. 

OCCLUDED  GASES. 

Though  occlusion  is  a  phenomenon  but  imperfectly  understood,  there 
appear  to  be  three  different  ways  in  which  it  is  manifested.  In  the  first 
of  these  the  absorption  seems  to  be  dependent  upon  porosity.  An  example 
of  this  is  charcoal,  one  variety  of  which  absorbs  172  volumes  of  ammonia, 

1  Analysis  No.  100. 


58  THE    GASES   IN   ROCKS. 

165  volumes  of  hydrogen  chloride,  97  volumes  of  carbon  dioxide,  and  2 
volumes  of  hydrogen.1  The  affinity  of  molten  silver  for  oxygen  illustrates 
another  phase  of  absorption  often  classed  as  occlusion.  It  has  long  been 
known  that  silver  absorbs  22  times  its  own  volume  of  oxygen  when  melted, 
but  gives  up  most  of  this  gas,  often  with  violence,  as  it  solidifies.2  This 
is  properly  a  solution  of  a  gas  in  a  liquid,  and  not  in  a  solid,  as  in  the  case 
of  true  occlusion.  The  third  type  is  the  absorption  of  gases  by  compact 
metals,  either  on  their  surface  or  within  their  mass,  such  as  the  occlusion 
of  hydrogen  by  palladium,  platinum,  and  iron.  This  is,  in  the  main,  inde- 
pendent of  porosity. 

Hydrogen  is  absorbed  by  these  metals  at  ordinary  temperatures,  but 
is  only  given  off  at  higher  temperatures.  This  principle  was  demonstrated 
by  Graham,  who  placed  a  thin  plate  of  palladium,  charged  with  hydrogen, 
in  a  vacuum  and  observed  that  at  the  end  of  two  months  the  vacuum  was 
still  perfect.  No  hydrogen  had  vaporized  in  the  cold,  but  on  the  applica- 
tion of  a  heat  of  100°  and  upwards,  333  volumes  of  gas  were  evolved  from 
the  metal.3  The  degree  of  heat  required  to  expel  hydrogen  absorbed  by 
platinum  and  iron  was  found  to  be  little  short  of  redness,  although  the 
gas  had  entered  the  metal  at  a  low  temperature.  Another  series  of  experi- 
ments by  the  same  investigator  showed  that,  to  be  occluded  by  palladium 
and  even  by  iron,  hydrogen  does  not  need  to  be  applied  under  sensible 
pressure,  but  on  the  contrary,  when  highly  rarefied,  it  is  still  freely  absorbed 
by  these  metals.  These  results  have  been  confirmed  by  Mond,  Ramsay, 
and  Shields,4  who  found  that  platinum  black  at  very  low  pressures  absorbed 
a  certain  quantity  of  hydrogen.  On  increasing  the  pressure  of  the  hydro- 
gen up  to  about  200  to  300  millimeters,  a  further  quantity  was  absorbed, 
but  beyond  this  point  an  increase  of  pressure  had  comparatively  little 
effect.  These  investigators  regarded  110  volumes  as  the  amount  of  hydro- 
gen really  occluded  by  platinum  black,  although  310  volumes  were  actually 
absorbed. 

Experiments  indicate  that  the  quantity  of  hydrogen  occluded  depends 
greatly  upon  the  condition  of  the  metal.  When  chemically  reduced,  cobalt 
may  occlude  59  to  153  volumes,  nickel  17  to  18,  and  iron  9  to  19  volumes.5 
Though  common  iron  wire  occludes  only  0.46  volume  of  hydrogen,8  this 
same  metal,  when  electrolytically  deposited,  may  absorb  nearly  250  vol- 
umes of  this  gas.7  The  maximum  quantity  of  hydrogen  occluded  by  any 
metal,  so  far  as  recorded,  is  982  volumes  absorbed  by  freshly  precipitated 
palladium.8  Dumas  has  shown  that  aluminum  heated  in  vacuo  to  1400° 
gives  off  more  than  its  own  volume  of  gas,  consisting  chiefly  of  hydrogen 
with  a  little  carbon  monoxide,  but  without  traces  of  carbon  dioxide,  oxygen, 
or  nitrogen.9  Under  the  same  conditions,  magnesium  rapidly  expels  1.5 

1  Barker,  Textbook  of  Physics,  p.  183. 

2  Chimie  Mine'rale,  Moissan,  t.  1,  p.  203. 

8  Graham,  Chemical  and  Physical  Researches,  pp.  283-290. 

4  Proc.  Roy.  Soc.,  vol.  58  (1895),  pp.  242-243. 

5  Chimie  Min6rale,  Moissan,  t.  1,  p.  51. 

8  Graham,  Chemical  and  Physical  Researches,  p.  279. 

7  Cailletet,  L'Institut,  Nouv.  Se>.,  Ann.  3,  p.  44. 

8  Graham,  Chemical  and  Physical  Researches,  p.  287. 
8  Dumas,  Comptes  Rendus,  90  (1880),  p.  1027. 


STATES    OF   THE    GASES. 


59 


volumes  of  nearly  pure  hydrogen.  Many  other  metals  behave  similarly. 
Non-metallic  substances  appear  to  possess  this  property  in  a  lesser  degree. 
Porcelain  occludes  hydrogen,  whether  because  of  its  porosity  or  solvent 
qualities  is  not  certain.  Quartz  is  said  to  be  penetrable,  at  high  tempera- 
tures, by  the  gases  from  the  oxyhydrogen  flame,1  which  points  towards  a 
form  of  occlusion. 

In  addition  to  hydrogen,  other  gases  are  occluded.  Litharge,  when  in 
the  molten  condition,  dissolves  hydrogen,  carbon  monoxide,  and  nitrogen, 
of  which  it  retains  a  portion  on  solidifying.2  Cast  iron,  on  cooling,  retains 
4.15  volumes  of  carbon  monoxide,3  which  perhaps  may  be  due  to  the  for- 
mation of  iron  carbonyl,  Fe(CO)4,  or  similar  unstable  compounds. 

Analyses  show  that  whenever  metallic  iron  is  present  in  notable  quan- 
tities carbonic  oxide  becomes  an  important  constituent  of  the  gas  evolved. 
The  following  analyses  of  the  gases  from  various  types  of  iron  indicate 
the  proportions  of  hydrogen,  carbon  monoxide,  carbon  dioxide,  and  nitro- 
gen which  this  metal  may  absorb,  given  in  percentages  of  the  total  gas 
content: 

TABLE  36. 


Iron. 

Analyst. 

H2. 

CO. 

C02. 

N2. 

White,  carbonaceous,  cast  iron  
Mild  steel  

Troost  & 
Hautefeuille1 
Parry 

74.07 
52.6 

16.76 
24.3 

3.59 
1655 

5.58 
65 

Ordinary  gray  charcoal  iron  

Cailletet 

3860 

4920 

1220 

Gray  coke  iron            

Do 

3270 

5790 

840 

Steel             

Troost  & 

Bessemer  steel  before  adding  spiegel  
Bessemer  steel  after  adding  spiegel 

Hautefeuille 
Muller  2 
Do 

22.27 
88.8 
770 

63.65 
0.7 

2.27 

11.36 
10.5 
229 

Open-hearth  steel    

Do 

678 

22 

308 

Cupola  pig  iron 

Do 

833 

25 

142 

Horseshoe  nail  heated  2  hours 

Graham  2 

350 

503 

77 

70 

Same  heated  2  hours  more 

Do 

210 

580 

210 

1  Cited  by  Cohen,  Meteoritenkunde,  p.  181. 

» Cited  by  Lane,  Bull.  Qeol.  Soc.,  vol.  5  (1894),  p.  264. 

Whatever  may  prove  to  be  the  ultimate  significance  of  occlusien,  and  in 
whatever  condition  these  gases  are  stored  in  the  iron,  whether  it  be  in  the 
nature  of  a  solution,  as  Mendele"ef  has  suggested,  or  as  definite  compounds — 
hydrides,  nitrides,  and  carbonyls — the  fact  remains  that  these  gases  exist 
within  the  metal  and  are  in  many  respects  similar  to  the  gases  locked  up  in 
iron  meteorites.  Fresh  iron  borings  from  the  interior  of  a  metallic  meteorite 
have  usually  been  assumed  to  be  free  from  any  hydration  or  carbonation 
from  terrestrial  agencies,  and  so  have  been  held  to  contain  true  meteoritic 
gases.  Some  question  respecting  this  belief  has  arisen  from  certain  analyses 
which,  as  we  have  seen,  indicate  secondary  action.4  In  addition  to  this 
the  gases  actually  received  in  the  laboratory  may  not  represent  the  original 

1  Poynting  and  Thomson,  Properties  of  Matter,  p.  204. 

2  Le  Blanc  and  Cailletet,  cited  by  Violle,  Cours  de  Physique,  t.  1,  p.  922. 

3  Daniell,  Principles  of  Physics,  p.  327. 

*  Experiments  with  the  Toluca  iron  ;  Analysis  No.  108. 


60  THE    GASES    IN    ROCKS. 

proportions  on  account  of  the  reducing  action  of  iron  on  carbon  dioxide 
and  water-vapor.  Meteorites  of  the  stony  type,  unless  absolutely  fresh, 
are  more  open  to  the  suspicion  of  terrestrial  hydration  and  carbonation. 
But  the  Allegan  meteorite  gathered  up,  still  hot,  within  five  minutes  of 
its  fall,  has  not  been  subjected  to  outdoor  exposure,  though  it  may  have 
absorbed  a  small  amount  of  moisture  and  carbonic  acid  from  the  atmo- 
sphere since  being  placed  in  the  National  Museum.  It  yielded  somewhat 
more  than  half  of  its  own  volume  of  gas.1  Fresh  material  from  the  interior 
of  the  Estacado,  Texas,  meteorite,  heated  in  a  vacuum  in  the  presence  of 
phosphorus  pentoxide  for  five  hours  at  150°,  and  then  allowed  to  remain 
untouched  for  several  days  to  enable  the  drying  agent  to  take  up  the  last 
traces  of  moisture  in  the  tubes,  still  yielded  at  red  heat  0.86  volume  of  gas, 
of  which  36.25  per  cent  was  hydrogen.2 

These  gases  from  stony  meteorites  resemble  those  from  some  igneous 
rocks.  That  this  correspondence  should  exist,  is  entirely  in  accordance 
with  the  view  that  meteorites  have  been  derived  from  the  disruption  of 
small  planetary  bodies  of  the  nature  of  the  asteroids.  As  in  the  meteorites, 
so  in  the  rocks,  that  portion  of  the  gases  which  can  not  have  been  produced 
by  chemical  reactions  at  elevated  temperatures,  nor  from  the  bursting 
of  rock-bound  cavities,  may  fairly  be  assigned  to  occlusion.  The  computa- 
tions indicating  the  excess  of  hydrogen  obtained  from  quartz  and  beryl 3 
over  that  which  might  have  arisen  from  the  interaction  of  iron  and  water 
under  the  most  generous  assumptions  show  that,  in  some  cases,  more  gas 
may  arise  from  a  state  of  occlusion  than  from  ordinary  chemical  action. 
The  amount  of  occluded  gases  may  be  actually  greater  than  that  indicated 
by  demonstrating  the  inadequacy  of  other  modes  of  holding  gas.  But  in 
basic  rocks  containing  hydrated  minerals  and  an  abundance  of  ferrous 
salts,  the  resulting  volumes  of  hydrogen  must  doubtless  come  largely  from 
the  decomposition  of  the  water  of  constitution,  and  the  amount  of  occluded 
gases,  if  any,  is  beyond  determination  by  these  methods. 

The  gases  argon  and  helium,  which,  according  to  current  chemical 
views,  do  not  form  compounds,  must  exist  within  rocks  either  mechanically 
entrapped  or  in  a  state  of  occlusion.  There  are  those,  notably  Ramsay 
and  Travers,  who  believe  in  the  combining  properties  of  argon  and  helium; 
but  the  balance  of  opinion  seems  to  be  on  the  other  side,  so  far  as  ordinary 
terrestrial  conditions  are  concerned.  Lord  Rayleigh  concludes  his  paper 
on  the  inactivity  of  these  two  gases,  with  this  sentence:  "There  is,  there- 
fore, every  reason  to  believe  that  the  elements,  helium  and  argon,  are  non- 
valent,  that  is,  are  incapable  of  forming  compounds."4 

As  the  chemists'  supply  of  helium  comes  from  certain  minerals,  chiefly 
those  containing  compounds  of  uranium,  its  occurrence  in  rocks  is  a  well- 
known  fact.  Recent  studies  have  revealed  the  existence  of  helium  in  beryl.5 
Argon  is  perhaps  more  widely  distributed  than  helium,  Gautier  having 
detected  this  element  in  ordinary  granite.  The  waters  of  many  springs 

1  Analysis  No.  106. 

2  Analysis  No.  107. 

3  Ante,  pp.  46-48. 

4  Lord  Rayleigh,  Proc.  Roy.  Soc.,  vol.  60,  p.  56. 
1  R.  J.  Strutt,  Nature,  Feb.  21,  1907,  p.  390. 


SIGNIFICANCE    OF   THE   THREEFOLD    STATE.  61 

bring  up  both  helium  and  argon,  proving  the  presence  of  considerable 
quantities  of  these  elements  within  the  earth.  This  rather  wide  distri- 
bution, when  taken  in  connection  with  their  supposed  chemical  inertness, 
strengthens  the  presumption  that  occlusion,  or  some  form  of  gas  diffusion, 
is  prevalent  in  rocks.  Though  of  much  interest  to  chemists  and  physicists, 
these  gases,  on  account  of  their  comparative  scarcity,  do  not  play  a  very 
important  r61e  in  general  geological  problems.  Their  presence  in  small 
quantities  within  the  rocks  of  the  earth's  crust  being  established,  quan- 
titative determinations  become  of  less  value.  In  the  analyses  made  for 
this  paper,  whose  prime  purpose  was  to  determine  the  range  and  distribu- 
tion of  the  common  gases,  the  separation  of  helium  and  argon  from  nitrogen 
was  not  usually  attempted.  These  gases  when  present  are  included  in 
the  figures  given  for  nitrogen.  In  the  case  of  pitchblende  and  carnotite, 
however,  helium  was  so  important  a  constituent  of  the  gas  that  its  pro- 
portions were  determined.  Carnotite  produced  1.28  per  cent  of  helium, 
amounting  to  0.04  volume,  while  pitchblende  gave  38.48  per  cent,  or  0.37 
volume.1  In  both  of  these  cases  nitrogen  also  was  abnormally  high. 

In  general,  therefore,  helium  and  argon,  together  with  at  least  as  much 
of  the  other  gases  as  can  be  shown  not  to  have  been  produced  by  chemical 
reactions  or  the  bursting  of  inclosing  walls,  are  to  be  attributed  to  occlusion 
or  some  form  of  diffusion  not  distinguishable  from  occlusion.  In  many, 
and  perhaps  most,  rocks  this  will  not  be  the  major  part,  for,  of  the  three 
gas-liberating  processes,  that  by  chemical  interaction  under  the  influence 
of  heat  appears  to  be  the  dominating  one. 

SIGNIFICANCE  OF  THE  THREEFOLD  STATE. 

GAS    IN   CAVITIES. 

While  chemical  reactions  and  the  phenomena  of  occlusion  imply  that 
gas  exists  in  the  interior  of  the  earth,  the  presence  of  gas  inclosed  in  cavi- 
ties under  great  pressure  adds  the  further  implication  that  the  gas  often 
exceeded  the  point  of  saturation  of  the  magma,  at  least  at  the  stage  of 
solidification.  Cavity  gases  are  most  abundant  in  minerals  of  poorly 
developed  cleavage,  pointing  perhaps  towards  a  strong  tendency  to  escape 
along  cleavage  planes  during,  or  after,  crystallization.  The  gas  inclusions 
in  quartz  may,  however,  owe  their  abundance  not  so  much  to  the  absence 
of  cleavage  as  to  the  fact  that  quartz  is  generally  the  last  mineral  to  crystal- 
lize out  of  a  magma,  and  hence  such  absorbed  gases  as  did  not  enter  into 
the  other  crystals  would  become  concentrated  in  the  siliceous  residue  and 
might  supersaturate  it. 

It  is  possibly  this  freely-moving  gas  above  the  point  of  saturation  which 
contributes  most  to  the  mobility  of  lavas.  Dissolved  gases  and  vapors, 
while  favoring  fluidity,  would  seem  to  be  relatively  less  effective.  But 
the  foregoing  investigations  imply  that  gases  mechanically  entrapped  in 
crystalline  rocks  are  not  very  abundant,  and  suggest  that  perhaps  the 
theory  of  liquidity  due  to  gas  is  overworked.  On  the  other  hand,  it  is 
true  that  as  the  lava  cooled  down  to  the  point  where  the  last  mineral  crys- 

1  Analyses  93  and  94. 


62  THE    GASES   IN   ROCKS. 

tallized,  its  gas-solvent  powers  would  be  increasing,  allowing  some  of  the 
gas  to  pass  into  solution.  At  the  same  time  free  gas  might  be  occluded  by 
the  growing  crystals.  The  experiments  upon  the  reabsorption  of  gas  by  ex- 
hausted rock  powder  indicate  that  a  portion  of  the  gas  unites  chemically  as 
the  heat  diminishes.  Because  of  these  processes,  liquid  lavas  may  be  sup- 
plied with  free  gas,  even  when  the  solidified  rocks  retain  but  little  free  gas. 

As  the  imprisoned  carbon  dioxide  frequently  remains  in  the  liquid 
form  up  to  the  critical  point  (30.9°  C.),  it  must  be  subjected  to  a  pressure 
of  at  least  73  atmospheres,  which  is  the  critical  pressure  of  this  gas.  Since 
a  pressure  of  73  atmospheres  corresponds  to  a  column  of  water  2,470  feet 
in  height,  quartz  crystals  formed  from  aqueous  solution,  under  hydrostatic 
pressure  simply,  can  not  contain  liquid  carbon  dioxide  up  to  30.9°  unless 
developed  at  depths  exceeding  2,470  feet.  It  is  to  be  recognized,  however, 
that  such  crystals  might  be  formed  at  lesser  depths  if  mechanical  pressure 
operated  with  hydrostatic  pressure  or  replaced  it. 

If  the  quartz  crystallized  from  a  lava,  say  at  1100°C.,  the  effect  of 
cooling  down  to  ordinary  temperatures  upon  both  the  size  of  the  cavity 
and  the  pressure  of  the  inclosed  carbon  dioxide  must  be  taken  into  account. 
If  we  take  the  case  of  a  cavity  found  to  be  entirely  filled  with  carbon  dioxide 
at  the  critical  point  (30.9°  C.  and  73  atmospheres),  it  is  possible,  by  the 
use  of  Van  der  Waal's  equation,  to  calculate  the  pressure  to  which  the  gas 
would  be  subjected  if  the  quartz  were  heated  to  1100°.  This  pressure  is 
found  to  be  756  atmospheres,1  provided  the  size  of  the  cavity  remains 
constant.  But  as  most  minerals  contract  on  cooling,  the  volume  of  the 
cavity  diminishes  at  the  same  rate  as  though  it  were  filled  with  the  material 
of  the  inclosing  walls.2  The  coefficient  of  expansion  of  quartz  is  given  as 
0.00003618.  Assuming  for  the  sake  of  simplicity  that  the  rate  of  expansion 
does  not  vary  greatly  with  changing  temperatures,3  quartz,  cooling  from 
1100°  to  31°,  would  contract  to  an  extent  of  about  3.87  per  cent  of  its 
original  volume.  Since  the  contraction  of  the  quartz  diminishes  the  size 
of  the  cavity  and  increases  the  pressure  by  3.87  per  cent,  the  original 
pressure  need  be  only  727  atmospheres,  which  corresponds  to  the  pressure 
beneath  9,100  feet  of  average  rock.  To  fill  cavities  forming  in  crystals  at 
1100°  with  carbon  dioxide  which  is  so  condensed  that  it  will  pass  into  the 
liquid  state  just  at  the  critical  temperature  when  the  rock  cools  down, 
a  pressure  corresponding  to  a  depth  of  at  least  9,100  feet,  or  its  mechanical 
equivalent,  would  seem  to  be  required.  If,  when  warmed  under  the  micro- 
scope, the  liquid  carbon  dioxide  is  found  to  pass  into  the  gaseous  state  at 
temperatures  below  30.9°,  and  the  cavity  contains  only  carbon  dioxide, 
or  carbon  dioxide  and  water,  these  must  have  been  entrapped  under  a 
pressure  less  than  727  atmospheres,  or  else  the  crystal  was  formed  at  a 
temperature  above  1100°. 

1  By  starting  with  the  equation  p  =  ~^~~2  at  the  critical  point  where  the  values 

of  the  constants  are  taken  as  #=0.003684;  a  =  0.00874;  6=0.0029;  v  =  36  =  O.OOS7, 
and  substituting  for  the  critical  temperature,  T= 1100°+ 273°,  the  theoretical  value  of  756 
atmospheres  for  the  pressure  at  1100°  is  obtained. 

2  Daniell,  Principles  of  Physics,  p.  379. 

3  It  would,  however,  slowly  increase  with  the  increase  of  temperature. 


SIGNIFICANCE    OF   THE    THREEFOLD    STATE.  63 

The  estimate  of  9,100  feet  for  the  minimum  depth  (where  weight  alone 
acts)  at  which  igneous  quartz  crystals  now  containing  carbon  dioxide, 
liquid  up  to  30.9°,  could  have  been  formed,1  applies  best  to  those  cases  in 
which  only  carbon  dioxide  exists  in  the  crystal  cavities.  If  there  are  other 
gases  and  liquids  present  in  appreciable  quantities,  this  figure  becomes  less 
applicable,  since  the  constants  a  (denoting  an  internal  force  or  attraction) 
and  6  (representing  the  sum  of  the  spheres  of  influence  of  all  the  molecules 
in  the  space  v)  used  in  Van  der  Waal's  equation  are  not  the  same  for 
all  gases.  At  how  much  greater  depths  than  this  the  crystallization  of  cer- 
tain specimens  of  quartz  actually  did  take  place,  if  rock  weight  alone  was 
involved,  may,  perhaps,  be  estimated  by  a  painstaking  determination  of 
the  pressure  under  which  the  imprisoned  carbon  dioxide  exists  in  these 
minute  cavities.  This  might  be  accomplished  by  piercing  one  of  the  larger 
cavities  while  submerged  in  mercury  or  other  liquid,  and  noting  the  expan- 
sion of  the  freed  bubble,  as  first  suggested  by  Sir  Humphry  Davy. 

Though  naturally  subject  to  limitations,  it  is  nevertheless  possible  to 
throw  considerable  light  upon  the  nature  of  cavity  inclusions  by  the  use 
of  the  microscope.  Some  of  the  conditions  may  be  stated: 

(1)  If,  at  slightly  under  30.9°,  the  cavity  is  entirely  filled  with  a  liquid 
which  completely  vaporizes  at  30.9°,  it  contains  only  carbon  dioxide. 

(2)  If,  at  slightly  under  30.9°,  the  cavity  is  filled  with  two  immiscible 
liquids,  one  of  which  passes  into  the  gaseous  state  at  30.9°,  the  liquids  are 
probably  water  and  carbon  dioxide. 

(3)  If  the  cavity,  when  just  below  30.9°,  contains  a  liquid  and  an  appre- 
ciable gas-bubble,  and  the  liquid  does  not  disappear  when  the  slide  is 
warmed  above  30.9°,  the  liquid  is  probably  water,  and  the  bubble  water- 
vapor  with  perhaps  some  of  the  difficultly  liquefiable  gases,  such  as  hydrogen, 
nitrogen,  or  methane. 

(4)  If,  as  is  often  the  case,  the  temperature  at  which  the  liquid  in  a 
cavity  disappears  is  found  to  be  several  degrees  below  the  critical  tempera- 
ture of  carbon  dioxide,  two  interpretations  are  possible:  either  the  carbon 
dioxide  is  subject  to  a  pressure  less  than  73  atmospheres,  or  else  there  is  a 
small  proportion  of  another  less  liquefiable  gas  present.    If  the  cavity  be 
opened  and  only  carbon  dioxide  be  found,  the  pressure  under  which  the 
gas  existed,  and  from  that  something  as  to  the  conditions  under  which 
the  crystal  was  formed,  can  be  computed  from  the  temperature  at  which 
the  liquid  disappeared.     If  another  gas,  such  as  hydrogen  or  nitrogen,  be 
found  and  identified,  it  is  possible,  by  using  an  equation,2  to  calculate  the 
relative  proportions  of  the  two  gases  from  the  critical  temperature  of  the 
mixture.     Thus  a  cavity  containing  a  mixture  of  carbon  dioxide  and 
nitrogen  which  had  a  critical  temperature  of  29°  would  hold  98.7  per  cent 

1  This  figure  is  based  on  the  assumption  that  the  quartz  crystallized  at  1100°;  if  it 
is  desired  to  use  other  temperatures,  they  can  be  substituted  in  Van  der  Waal's  equation 
and  the  corresponding  pressures  computed. 

2 t  ^  trft  +  (100-n)^  where  t  jg  the  Ob8erve(i  critical  temperature  of  the  mixture,  tt 

and  <2  are  the  theoretical  critical  temperatures  of  the  two  liquefied  gases.  Then  n  equals 
the  proportion  by  weight  of  the  first  liquid  and  100 -n  equals  the  proportion  by  weight 
of  the  second  liquid. 


64  THE    GASES   IN    ROCKS. 

of  the  former  and  1.3  per  cent  of  the  latter.  A  critical  temperature  of  28° 
would  indicate  98.1  per  cent  of  liquid  carbon  dioxide  and  1.9  per  cent  of 
liquid  nitrogen,  while  27°  would  mean  97.5  per  cent  of  the  dioxide  and  2.5 
per  cent  nitrogen.  The  figures  for  carbon  dioxide  and  hydrogen  are  of  the 
same  general  order.  In  the  estimates  of  the  depths  at  which  cavity-bearing 
crystals  were  formed,  made  by  different  methods,1  it  has  been  usual  to 
assume  that  only  the  pressure  arising  from  the  weight  of  the  overlying  rock 
was  involved. 

Sorby  examined  those  cavities  which  contained  only  water,  or  a  saline 
solution,  and  a  vacuole  left  by  the  contraction  of  the  liquid,  as  a  result  of 
the  lowering  of  the  temperature.  By  noting  the  relative  size  of  the  bubble 
and  the  volume  of  the  liquid,  he  estimated  the  temperature  to  which  the 
mineral  would  have  to  be  heated  for  the  liquid  to  completely  fill  the  cavity, 
and  from  this,  together  with  the  elastic  force  of  the  water-vapor,  he  com- 
puted the  necessary  existing  pressure  in  feet  of  rock.  The  highest  tempera- 
ture found  by  this  method  was  only  356°  C.,  at  which  point  Sorby  believed 
that  the  trachyte  of  Ponza  solidified,  while  the  lowest  temperature  was 
89°  C.,  obtained  from  a  study  of  the  main  mass  of  granite  at  Aberdeen. 
But  Sorby  considered  it  more  probable  that  the  granite  crystallized  at 
about  the  same  temperature  as  the  trachyte  and,  assuming  that  the  solidifi- 
cation took  place  at  360°,  he  computed  that  the  granite  of  Aberdeen  was 
formed  under  a  pressure  of  78,000  feet  of  rock.2  These  estimates  are  based 
upon  the  unwarranted  supposition  that  when  the  crystals  were  formed 
the  volume  of  liquid  water  was  such  as  to  just  fill  the  cavities,  and  that  in 
each  case  a  meniscus  at  once  appeared  with  a  loss  of  heat.  He  overlooked 
the  fact  that  the  meniscus  could  not  appear  until  the  water  reached  the 
liquid  condition,  no  matter  at  what  temperature  the  growing  crystal  sur- 
rounded the  vesicle  of  highly  compressed  water-gas. 

The  highest  temperature  at  which  a  vacuole  of  this  sort  can  appear 
must,  therefore,  be  the  critical  temperature  for  water,  or  365°  C.  In  order 
to  study  this  problem,  we  may,  perhaps,  best  take  the  special  case  in  which 
the  inclosed  water  passed  through  its  critical  state  (at  365°  and  200.5 
atmospheres  pressure)  during  the  cooling  of  the  crystal.  The  vesicle  formed 
in  this  case  may  be  termed  the  critical  vacuole.  It  may  be  assumed  that 
the  growing  crystal  inclosed  the  water  at  some  temperature  in  the  neigh- 
borhood of  1100°,  which  is  an  average  temperature  for  the  solidification  of 
lavas.  Starting  thus  with  a  cavity  formed  at  1100°,  in  order  to  allow  the 
water  on  cooling  to  pass  through  the  critical  state,  an  original  pressure 
of  1,070  atmospheres  is  necessary  according  to  Van  der  Waal's  equation,3 
provided  the  size  of  the  cavity  remained  constant.  But  if  2.66  per  cent  is 
allowed  for  the  shrinkage  of  the  cavity  while  cooling  down4  from  1100° 

1  See  Geikie's  Textbook  of  Geology,  vol.  1,  pp.  144-145. 
>  Sorby,  Quart.  Jour.  Geol.  Soc.  London,  vol.  14,  p.  494. 

SP=~^T—  ^r-    In   this   case   the   values  of  the   constants   for   the   critical  point 

were  taken  to  be  /2  =  .003607:    a  =  .01173;    6  =  .00151;   v=36  =  .00453.     By  substituting 
for  the  critical  temperature,  T  =  1 100  +  273,  the  equation  gives  the  theoretical  value  of 
1,070  atmospheres. 
4  Ante,  p.  62. 


SIGNIFICANCE    OP   THE   THREEFOLD    STATE.  65 

to  365°,  the  original  pressure  need  be  only  approximately  1,040  atmospheres, 
a  pressure  which  corresponds  to  13,000  feet  of  rock  approximately. 

In  this  critical  case  the  meniscus  appears  as  soon  as  the  temperature 
falls  below  365°.  Since  pressure  exerts  but  little  influence  on  the  volume 
of  liquids,  the  shrinkage  of  the  water  in  the  cavity,  and  hence  the  growth  of 
the  gas-bubble,  is  largely  a  function  of  the  fall  in  the  temperature,  and,  with 
a  knowledge  of  the  varying  coefficient  of  expansion,  the  relation  between  the 
size  of  the  bubble  and  the  volume  of  the  liquid  could  be  computed  for  any 
temperature.  The  correction  for  the  constriction  of  the  cavity  between 
365°  and  20°  amounts  to  a  little  more  than  one  per  cent,  which  is  to  be 
added  to  the  size  of  both  the  cavity  and  the  vacuole  in  computation. 

If  these  principles  be  true,  a  vapor-bubble  relatively  smaller  than  the 
critical  vacuole  may  be  interpreted  to  mean  that  the  meniscus  did  not  appear 
in  the  cavity  until  the  crystal  had  cooled  below  the  critical  temperature, 
i.  e.,  that  at  this  temperature  the  water  was  more  than  normally  condensed, 
owing  to  a  pressure  exceeding  the  critical  pressure.  On  the  other  hand, 
a  vapor-bubble  relatively  larger  than  the  critical  vacuole  means  that, 
although  it  did  not  appear  until  below  365°,  it  began  as  a  sizable  vesicle 
when  it  did  start,  owing  to  the  lower  pressure  and  more  rarefied  condition 
of  the  water-gas. 

On  the  basis  of  his  experiments,  Sorby  estimated  that  a  vesicle  amount- 
ing to  28  per  cent  of  the  volume  of  the  liquid  in  the  cavity  would  vanish 
when  the  water  was  heated  to  340°  C.  According  to  this  figure,  a  vacuole 
occupying  in  the  neighborhood  of  30  or  35  per  cent  of  the  volume  of  the 
liquid  should  correspond  to  a  shrinkage  of  the  water  from  the  critical 
point  to  ordinary  temperatures.  But  this  figure  has  not  been  confirmed 
by  other  investigators.  Unfortunately  the  figures  obtainable  for  the  ex- 
pansion of  water  up  to  the  critical  point  vary  within  such  wide  limits  that 
it  does  not  seem  advisable  at  the  present  time  to  attempt  to  calculate  the 
relative  sizes  of  the  critical  vacuole  and  the  inclosing  liquid. 

The  difficulties  involved  in  applying  these  principles  are  considerable. 
Zirkel  has  pointed  out  that,  even  in  cavities  within  the  same  crystal,  there 
is  much  variation  in  the  relative  volume  of  the  vapor-bubble  and  the 
liquid,  from  which  the  inference  is  drawn  that  the  vapor-bubbles  are  due 
to  causes  other  than  contraction  on  cooling.1  Before  this  conclusion  can 
be  accepted  with  confidence,  due  consideration  must  be  given  to  the  loca- 
tion of  the  cavities  within  the  crystal,  and  also  to  the  evidence  that  they 
are  all  primary  inclusions.  In  an  ascending  lava  subject  to  a  steadily 
diminishing  pressure,  those  cavities  formed  during  the  early  stages  of 
crystallization  may  be  developed  under  conditions  quite  different  from  the 
cavities  later  inclosed  in  the  outer  parts  of  the  crystals.  If  systematic 
differences  in  the  cavities  can  be  found  to  correspond  with  variations  in 
their  location,  something  might  be  learned  of  the  history  of  the  lava  during 
the  period  of  crystallization.  Secondary  fluid  inclusions,  formed  subse- 
quent to  the  solidification  of  the  magma,  must  obviously  be  recognized 
and  avoided,  whenever  possible,  in  attempting  to  estimate  the  conditions 
under  which  crystallization  took  place. 

1  Zirkel,  cited  by  Geikie,  Textbook  of  Geology,  1,  p.  145. 


66  THE    GASES   IN   ROCKS. 

A  difficulty  of  a  more  serious  nature,  apparently,  suggested  by  Professor 
Iddings,  lies  in  the  change  of  volume  of  the  magma  in  the  passage  from  the 
liquid  to  the  crystalline  form.  Some  magmas,  such  as  those  of  granitic 
rocks,  contract  so  appreciably  upon  crystallization  that  it  is  conceivable 
that  the  last  crystals  to  form,  those  of  quartz  (which  also  contain  the  most 
liquid  and  gas  inclusions)  might  crystallize  under  reduced  pressures  in 
spaces  inclosed  by  crystals  of  the  minerals  already  formed.  The  relative 
size  of  the  bubble  of  vapor  in  the  cavity  and  the  accompanying  liquid 
would,  in  such  cases,  not  correspond  directly  to  the  depth  beneath  the 
surface  at  which  crystallization  took  place,  even  when  nothing  but  hydro- 
static pressure  affected  the  lava  column. 

In  the  present  defective  state  of  knowledge  as  to  the  modes  and  condi- 
tions which  obtain  in  lavas  penetrating  the  shell  of  the  earth,  it  is  by  no 
means  safe  to  assume  that  the  pressures  to  which  an  igneous  intrusion  is 
subject  are  merely  those  represented  by  the  overlying  rock  or  a  lava 
column  reaching  to  the  surface.  An  ascending  tongue  of  lava  may  extend 
to  great  depths  and  be  affected  by  pressures  brought  to  bear  upon  it  in  its 
lower  part,  which  might  be  in  excess  of  those  represented  by  the  depth  of 
the  head  of  the  column,  to  an  unknown  degree.  So  also  it  is  possible  that 
lavas  may  become  involved  in  mechanical  deformations  and  thus  be  subject 
to  special  pressures  in  no  close  correspondence  to  their  depth. 

WATER   AND    HYDROGEN. 

The  reversible  reactions  involving  hydrogen,  water,  and  iron  com- 
pounds, which  cause  uncertainties  in  the  extraction  of  gases  by  heat, 
are  also  operative  within  the  earth.  In  the  laboratory,  when  either  ferrous 
salts  and  water,  or  ferric  compounds  and  hydrogen,  are  heated  in  tubes 
without  the  removal  of  the  products,  reversible  reactions  set  in  until  a 
condition  of  equilibrium  is  established.  Hydrogen  and  water,  ferrous  and 
ferric  salts  are  all  present  in  a  state  of  balance.  In  the  interior  of  the  earth 
the  heated,  though  solid,  rocks  should,  it  would  seem,  behave  similarly, 
though  hindered  by  the  slowness  of  diffusion.  Nor  should  liquid  magmas 
constitute  any  exception  to  the  law.  Both  hydrogen  and  water-gas,  theo- 
retically, should  be  present  in  liquid  magmas  and  heated  solid  rocks.  The 
chief  uncertain  factors  are  high  temperatures,  and  pressures. 

The  effect  of  pressure  on  chemical  equilibrium  is  to  favor  the  formation 
of  that  system  which  occupies  the  smaller  volume,  but  if  there  is  no  change 
in  volume,  in  passing  from  one  system  to  the  other,  the  increase  of  pressure 
presumably  has  no  influence  on  equilibrium.1  In  the  reaction 

3FeO+H2O  ±^  Fe,O4+H2 

considered  as  a  thermochemical  equation,  the  number  of  gaseous  mole- 
cules, and  hence  the  volume  of  gas,  always  remains  the  same,  so  that  it 
is  not  likely  that  this  action  will  be  influenced  by  change  of  pressure.  A 
rise  of  temperature  favors  the  formation  of  that  system  which  absorbs 
heat  when  it  is  formed.2  A  comparison  of  the  amount  of  heat  liberated  by 
oxidizing  three  molecules  of  FeO  to  Fe3O4  and  one  molecule  of  H2  to  H2O 

1  Jones,  Physical  Chemistry,  p.  514. 

3  Van't  Hoff,  Lectures  on  Theoretical  and  Phys.  Chem.,  Pt.  1,  pp.  161-164. 


SIGNIFICANCE    OF   THE   THREEFOLD   STATE.  67 

shows  that,  in  the  former  case,  73,700  calories  are  evolved,  and  in  the 
latter  58,300;  that  is,  3FeO-fH2O — »- Fe3O4  +  H2  +  15,400  calories.  As 
heat  is  evolved  in  this  process,  a  rise  of  temperature  would  accelerate  the 
reaction  in  this  direction  less  than  the  reverse.  In  other  words,  the  higher 
the  temperature,  the  more  would  the  formation  of  ferrous  oxide  and  water 
be  favored  as  compared  with  the  conditions  at  lower  temperatures. 

Because  of  this,  there  is  much  reason  to  suppose  that,  at  the  depths 
where  lavas  originate,  hydrogen  and  oxygen  exist  combined  as  water, 
since  up  to  temperatures  of  2000°  C.,  the  dissociation  of  water  takes  place 
only  to  a  limited  extent.  If  a  state  of  equilibrium  between  hydrogen, 
water,  and  the  iron  compounds  were  established  in  the  heated  interior 
where  a  magma  originated,  as  soon  as  it  commenced  its  way  upward  and 
began  to  lose  heat  the  condition  of  equilibrium  would  be  destroyed.  With 
the  falling  temperature,  the  tendency  to  reestablish  equilibrium  would 
favor  the  formation  of  that  system  which  was  produced  with  the  libera- 
tion of  heat,  t.  e.,  magnetic  oxide  and  free  hydrogen.  In  ascending  lavas 
which  are  losing  heat,  the  tendency,  therefore,  is  to  produce  hydrogen  and 
magnetite,  or  ferroso-ferric  compounds.  This  is  doubtless  an  important 
source  for  the  hydrogen  which  is  so  copiously  exhaled  during  a  volcanic 
eruption.  At  the  same  time,  this  process  accounts  for  the  widespread 
occurrence  of  magnetite  in  igneous  rocks.  The  considerable  deposits  of 
magnetite,  formed  apparently  from  magmatic  segregation,  which  are  com- 
mon in  various  regions,  may,  perhaps,  owe  their  origin  to  a  combination  of 
causes,  in  which  this  equilibrium  reaction  is  an  important  factor. 

In  general,  these  reversible  reactions  tend  to  show  that  it  is  but  a  short 
step  from  hydrogen  to  water,  and  from  carbon  dioxide  to  monoxide,  and 
vice  versa,  and  that  all  of  these  must  occur  within  the  earth  owing  to  the 
processes  tending  toward  equilibrium.  Whether  hydrogen,  in  a  particular 
case,  occurs  in  the  magmas  in  the  free  state,  or  in  the  form  of  water-gas, 
therefore  becomes  relatively  unimportant.  Because  of  this  variation  of 
state,  the  problem  becomes  more  complex  and  broader  in  scope.  For  the 
most  part,  these  water-gases  are  to  be  regarded  as  truly  magmatic,  and 
not  derived  from  surface-waters  penetrating  to  the  liquid  lavas,  as  will 
be  brought  out  later.  They  are  here  put  forward  as  essential  factors  in 
the  evolution  of  the  magmas  from  the  original  planetary  matter. 

The  reactions  working  towards  equilibrium  are  able  to  supply  hydro- 
gen and  carbon  monoxide  under  conditions  favorable  to  their  absorption 
and  retention,  even  if  they  were  not  originally  present  as  occluded  gases. 
The  sources  of  the  gases  obtained  from  rocks  are  so  complex  that  it  is 
difficult  to  determine  how  much  is  to  be  assigned  to  each.  Because  of  the 
penetration  of  surface-waters  containing  carbonic  acid  in  solution,  through- 
out the  accessible  rocks  of  the  earth's  exterior,  it  is  likely  that,  in  many 
cases,  the  bulk  of  the  gas  obtained  by  heating  powders  in  vacuo  has  been 
derived  from  acquired  water  and  carbonated  compounds.  But  in  fresh 
meteorites,  which  presumably  have  not  been  subjected  to  action  of  this 
sort,  occlusion  is  relatively  more  important. 

From  the  constitution  of  meteorites,  some  of  the  principles  of  early 
terrestrial  evolution  may,  perhaps,  be  inferred,  though  the  growth  of  the 


68  THE    GASES   IN   BOCKS. 

earth  was  probably  not  quite  analogous,  in  all  respects,  to  the  formation 
of  the  meteorites.  Whether  we  take  the  meteoritic  material  to  repre- 
sent the  heavier  part  of  the  original  matter  of  the  solar  system,  or  the 
stellar  system,  as  a  whole,  matters  little  in  the  geologic  problem.  If,  in 
truth,  the  unoxidized,  heterogeneously  aggregated  material  of  meteorites 
be  typical  of  the  original  heavy  material  of  the  earth,  it  becomes  evident 
that,  in  the  case  of  our  planet,  other  factors  have  been  at  work  which  are 
not  operative  in  the  bodies  of  which  the  meteorites  are  supposed  to  be 
fragments.  These  visitors  from  space  are  characterized  by  such  minerals 
as  cohenite,  (Fe,Ni,Co)3C,  lawrencite,  FeCl2,  oldhamite,  CaS2,  and  schreib- 
ersite,  (Fe,Ni;Co)3P,  which,  next  to  nickel-iron,  is  the  most  widely  distributed 
constituent  of  iron  meteorites,1  though  of  less  importance  in  the  stony 
specimens.  Such  compounds  imply  an  absence  of  both  free  oxygen  and 
water  in  notable  quantities.  Of  like  import  is  the  absence  of  hydrated 
minerals,  such  as  micas  and  amphiboles.  Water  and  an  oxygenated  atmo- 
sphere appear  to  be  the  agents  which  are  lacking  in  the  bodies  from  which 
the  meteorites  were  derived,  but  which  have  been  the  operative  factors  in 
working  over  the  outer  portion  of  the  earth. 

But  the  original  source  of  the  earth's  atmosphere  and  hydrosphere 
is  taken  to  be  gas  occluded,  or  absorbed,  in  the  primitive  meteoritic  material. 
These  original  gases,  escaping,  furnished  both  atmosphere  and  hydrosphere 
when  the  earth  became  of  sufficient  size  to  retain  them.  A  self-regulating 
system  was  inaugurated.  In  the  early  stages  of  the  hydrosphere,  when 
growth  by  infalling  planetesimals  was  rapid,  much  water  was  buried 
within  the  fragmental  crust.  This  material,  worked  over  by  volcanic 
activity,  brought  to  the  surface  and  subjected  to  weathering  and  erosion, 
and  buried  beneath  more  material,  has  undergone  assortment  and  altera- 
tion until  the  accessible  rocks  at  the  present  time  are  very  different  from 
the  meteoritic  matter.  Since  the  earth  attained  its  growth  and  the  infall 
of  planetesimals  slackened,  much  less  water  has  penetrated  to  great  depths 
below  the  surface.  Post-Archean  sedimentaries  have  not  yet  reached 
thicknesses  sufficient  to  carry  inclosed  water  down  to  the  depths  from 
which  the  lavas  arise.  Deep  mines  indicate  that  fractures  and  fissures 
do  not  convey  water  down  to  very  great  depths  at  the  present  time.  If 
water  does  not  penetrate  so  rapidly  now,  and  hydration  and  carbonation 
are  less  effective,  it  is  also  probably  true  that  subsiding  vulcanism  brings 
less  gas  to  the  surface. 

It  is  essentially  a  system  of  balance.  At  the  same  time  that  water  is 
being  buried  with  sediment,  its  elements,  hydrogen  and  oxygen,  the  latter 
in  the  form  of  the  oxides  of  carbon,  are  exhaled  from  the  earth's  interior 
through  volcanic  outlets.  But  the  system  here  suggested  is  very  different 
from  the  postulated  limited  cycle  of  underground  water  which,  following 
DaubreVs  famous  experiment,2  has  crept  into  geologic  literature  as  the 
origin  of  volcanic  vapors  and  the  modus  operandi  of  vulcanism.  Instead 
of  surface-waters  following  cracks  and  fissures  down  to  the  hot  lavas  there 
to  be  absorbed,  the  water  already  is  present,  and  is  a  part  of  the  rocks  and 

1  Farrington,  Jour,  of  Geol.,  vol.  9,  pp.  405-407  and  525-526. 

2  Daubree,  Etudes  Synth&iques  de  Geologic  Expgrimentale,  t.  1,  pp.  236-246. 


VULCANISM.  69 

magmas  in  the  interior,  whether  actually  combined  as  water,  or  as  its 
elements  held  in  solution,  or  chemically  united  in  other  compounds.  These 
gaseous  elements  form  an  integral  part  in  the  magmas,  having  been  vital 
factors  in  their  development  from  the  primitive  planetary  matter.  That 
this  process  of  reworking  has  gone  on  to  considerable  depths,  if  we  are  to 
start  with  typical  meteoritic  material,  is  evidenced  by  the  fact  that  the 
deep-seated  plutonic  rocks  are  characterized  by  micas  and  other  hydrous 
minerals,  while  mineral  species  of  the  meteoritic  type  are  absent.1 

The  more  restrictive  phase  of  the  problem  of  water  will  be  discussed 
under  the  head  of  vulcanism. 

VULCANISM. 

In  the  actual  dynamics  of  vulcanism,  provided  the  gases  are  original 
in  the  magmas,  the  state  in  which  they  occur  is  not  of  vital  importance, 
except  in  so  far  as  it  determines  the  conditions  under  which  the  gases  be- 
come free,  from  occluded  or  chemical  bonds,  to  perform  their  part  in  the 
mobility  of  lavas,  in  the  explosions  which  sometimes  accompany  erup- 
tions, and  in  the  phenomena  of  fumaroles  and  volcanic  vents.  The  dis- 
tinction between  cavity,  occluded,  and  chemically  united  gas,  which  is 
made  in  the  case  of  solid  igneous  rocks,  can  not  be  extended  to  the  liquid 
lavas.  In  the  liquid  lava  the  gas  may  be  supposed  to  be  imprisoned 
mechanically,  or  else  to  form  a  part  of  the  magmatic  solution.  On  the 
solidification  of  the  mass,  the  gas,  formerly  existing  in  the  free  state,  may 
enter  chemical  combinations  at  the  lower  temperature,  may  be  occluded 
by  the  solid  rock,  or  may  become  entrapped  within  the  minerals  last  to 
crystallize.  So,  too,  it  is  possible  that  some  of  the  gas  dissolved  in  the 
magma  may,  because  of  cooling  and  crystallization  of  adjacent  portions 
of  the  solution,  reach  a  supersaturated  condition  and  appear  in  the  solid 
rock  also  as  gas  inclusions.  Otherwise,  it  would  pass  into  the  solid  rock 
occluded  or  chemically  combined.  The  condition  of  the  gases  examined 
in  the  laboratory  need  not,  necessarily,  correspond  to  a  particular  state 
of  occurrence  in  the  lava  before  crystallization. 

Gases  mechanically  distributed  throughout  the  lava  would  always  be 
an  operative  factor  in  vulcanism,  while  such  gases  as  were  chemically 
combined  in  the  solution  would,  presumably,  only  become  free,  and  hence 
fully  operative,  upon  the  lowering  of  the  temperature  and  the  relief  of 
pressure,2  and  probably  but  partially  then.  Since  vapors  and  gases  in  the 
free  state  are  the  cause  of  volcanic  explosions,  they  can  be  traced  as  far 
down  in  the  conduits  as  explosions  occur.  From  the  nature  of  these  explo- 
sions, which  appear  to  be  due  to  the  accumulation  of  vapor  gradually  work- 
ing upward  until  suddenly  able  to  relieve  itself,  it  is  fair  to  suppose  that 

1  This  statement  should  perhaps  be  qualified.     The  basalt  at  Ovifak,  Greenland, 
contains  iron  strongly  resembling  the  meteoric  metal,  and  in  which  the  minerals  cohenite, 
lawrencite,  and  doubtfully  schreibersite  have  been  recognized.     The  occurrence  of   this 
terrestrial  iron  would  indicate  that  material  of  this  sort  still  occurs  at  points  within  the 
outer  part  of  the  earth. 

2  A  falling  temperature  favors  the  liberation  of  hydrogen  from  water  by  ferrous 
compounds  (see  p.  67),  while  carbonates  are  most  easily  decomposed  at  low  pressures 
(see  p.  49). 


70  THE    GASES   IN   ROCKS. 

aqueous  vapor  and  the  auxiliary  gases  are  present  in  the  free  state  at 
still  greater  depths. 

It  has  been  the  observation  of  those  who  have  studied  volcanic  erup- 
tions that  water- vapor  is  by  far  the  most  abundant  of  the  gaseous  products 
of  volcanoes.  Water  is  also  the  principal  compound  of  the  element  hydro- 
gen, which  is  quantitatively  the  most  important  gas  obtained  by  heating 
igneous  rocks  in  vacuo.  According  to  one  of  the  common  theories  of 
vulcanism,  it  is  water,  circulating  underground  and  necessarily  dissolving 
and  absorbing  mineral  and  gaseous  material,  which  penetrates  to  the 
lavas  and  gives  to  them  their  supply  of  vapor  and  gases.  Water,  then,  is 
a  critical  element  in  the  theories  of  vulcanism,  and  likely  to  be  a  decisive 
factor,  upon  the  basis  of  which  many  of  these  theories  may  stand  or  fall. 
It  is,  therefore,  of  great  importance  to  know  whether  the  aqueous  vapor, 
which  is  so  copiously  exhaled  from  volcanic  vents  and  plays  such  a  r61e  in 
vulcanism,  is  derived  originally  from  the  magmas,  or  is  merely  underground 
water  which  has  been  incorporated  by  the  lava  in  its  journey  upward.  A 
decision  of  this  question  will  carry  with  it  the  solution  of  the  allied  question 
concerning  the  ultimate  source  of  the  other  gases,  and  also  throw  much 
light  upon  some  of  the  more  comprehensive  theories  of  vulcanism. 

Appealing  to  the  fact  that  chlorine,  in  the  form  of  hydrochloric  acid 
and  volatilized  chlorides,  is  one  of  the  products  of  volcanoes,  one  of  the 
standard  hypotheses  attributes  the  cause  of  vulcanism  to  the  penetration 
of  sea-water  to  the  heated  interior.  If  this  were  so,  isolated  volcanoes 
far  out  at  sea  would  be  expected  to  yield  much  more  chlorine  than  those 
on  the  continents.  But  the  Hawaiian  volcanoes  exhale  comparatively 
little  chlorine  or  sublimed  chlorides.  It  has  been  claimed  that  rain-water, 
sinking  into  the  cone,  would  have  sufficient  head  to  exclude  the  sea-water 
from  the  neighborhood  of  the  hot  lava.  Rain,  however,  falls  upon  but  a 
small  part  of  the  whole  cone,  whose  greater  portion  is  under  the  sea.  It 
would  seem  that  if  rain-water,  falling  upon  a  cone  built  up  from  the  ocean 
bottom,  is  able,  by  means  of  its  head,  to  keep  out  the  sea-water  which 
covers  the  lower  slopes,  the  same  amount  of  water  precipitated  upon  a 
continental  volcano  would  be  even  more  efficient  in  preventing  the  general 
underground  water  from  coming  in  contact  with  the  lava  in  the  conduit. 
Whatever  may  be  the  reason  for  the  small  amount  of  chlorine  given  off 
by  the  volcanoes  of  Hawaii,  sea-water  does  not  reach  the  heated  lavas  in 
sufficient  quantities  to  affect  them  appreciably. 

On  account  of  the  pressure  exceeding  the  crushing  strength  of  the 
rock,  pores  and  crevices  can  not  exist  at  depths  greater  than  30,000  feet 
according  to  the  most  generous  estimate,1  and  it  is  probable  that  continu- 
ous cracks  cease  much  short  of  this.  Beyond  this  extreme  figure,  meteoric 
waters  can  not  be  regarded  as  of  any  quantitative  importance,  on  account 
of  the  extreme  slowness  of  diffusion  through  solid  bodies  not  containing 
minute  fractures.  Liquid  carbon  dioxide  still  existing  under  great  pres- 
sure in  sand  grains  of  Pre-Cambrian  age  is  a  concrete  example  of  this 
slowness.  While,  theoretically,  water  may  extend  downward  to  the  limit 
of  the  zone  of  fracture,  the  testimony  of  deep  mining  appears  to  show  that 

1  Hoskins,  16th  Ann.  Kept.  U.  S.  Geol.  Surv.,  p.  853. 


VULCANISM.  71 

meteoric  waters  grow  relatively  scant,  as  a  rule,  below  the  uppermost 
1,500  to  1,800  feet  of  the  earth's  crust.1  This  shallowness  of  meteoric  water 
increases  the  difficulties  encountered  by  the  hypothesis  that  the  lava  beds 
are  supplied  from  this  source,  since  they  rise  from  far  greater  depths  and 
only  the  upper  portions  of  their  conduits  would  be  exposed  to  these  waters. 

It  is  in  this  portion  of  the  zone  of  fracture  that  DaubreVs  much  quoted 
experiment  upon  the  Strasbourg  sandstone  2  finds  its  application,  if  any- 
where, since  numerous  capillary  pores  with  plenty  of  water  are  requisites 
for  the  operation  of  this  principle.  This  famous  experiment  demonstrated 
that,  owing  to  its  force  of  capillarity,  boiling  water  will  pass  through  a 
disk  of  sandstone,  2  centimeters  in  thickness,  against  a  slight  steam-pres- 
sure on  the  other  side.  But  it  was  only  necessary  for  the  steam-pressure 
to  reach  685  millimeters,  or  nine-tenths  of  an  atmosphere,  in  order  to 
prevent  any  more  water  from  passing  through  the  sandstone.  It  is  a  long 
jump  from  this  trivial  capillary  force,  equal  to  less  than  one  atmosphere 
of  steam-pressure,  to  the  great  pressures  which  would  have  to  be  overcome 
in  the  depths  of  the  earth's  crust  in  order  to  reach  the  hot  lavas,  even  though 
it  be  allowed  that  the  water-vapor,  if  it  came  in  contact  with  the  lava, 
would  be  absorbed.  Capillary  force  seems  quantitatively  inadequate. 

To  reach  the  critical  pressure  of  water  due  to  the  hydrostatic  column, 
it  is  necessary  to  penetrate  the  earth  to  a  depth  of  about  6,900  feet.  At 
depths  less  than  this,  water  passing  into  the  vaporous  condition,  in  the 
neighborhood  of  hot  volcanic  conduits,  at  temperatures  below  the  critical 
point,  should  leave  behind  more  or  less  of  the  matter  held  by  it  in  solution, 
since  the  condensation,  and  hence  molecular  attraction  of  the  vapor  for 
solutes,  is  less  than  that  of  the  water.  Thus  even  if  vapor  from  underground 
waters  should  enter  the  lavas,  as  Daubre*e  has  suggested,  in  the  outer 
6,900  feet  of  the  earth's  crust,  much  of  the  chlorides,  sulphates,  carbonates, 
and  silicates,  dissolved  in  the  water,  would  have  been  left  behind.  At 
depths  between  6,900  feet  and  25,000  feet,  beyond  which  water  can  not 
penetrate,  owing  to  the  closure  of  all  pores  by  the  pressure  of  superin- 
cumbent rock,  mineral  matter  dissolved  in  the  water  would  probably  still 
remain  in  solution  when  the  liquid  passed  into  the  gaseous  state  at  the 
critical  temperature,  since  the  density  of  the  gas  is  equal  to,  or  greater 
than,  that  of  the  liquid. 

The  lava,  being  under  considerable  pressure,  may  be  supposed  to  occupy 
all  the  cracks  and  crevices  in  the  adjacent  rocks,  except  those  of  capillary 
dimensions.  If,  therefore,  in  the  passage  of  underground  water  into  vapor, 
preparatory  to  entering  lavas  in  the  outer  6,900  feet  of  the  earth's  crust, 
much  of  the  dissolved  mineral  matter  be  deposited  in  the  minute  pores 
leading  to  the  lava,  they  should  quickly  become  sealed,  preventing  any 
further  access,  even  of  water,  to  the  lava.  To  test  this  principle  experi- 
mentally, a  cylinder  of  medium-grained  Potsdam  sandstone  from  Wis- 
consin, 40  millimeters  in  diameter  and  28  millimeters  in  thickness,  was 
soldered  into  a  short  piece  of  iron  piping,  fitted  at  one  end  with  an  elbow 

1  Kemp,  Economic  Geol.,  vol.  2  (1907),  p.  3;  Finch,  Proc.  Col.  Sci.  Soc.,  vol.  7  (1904), 
pp.  193-252. 

2  DaubrSe,  Etudes  Synthe~tiques,  t.  1,  pp.  236-246. 


72  THE    GASES   IN    ROCKS. 

to  serve  as  a  receptacle  for  water,  and  at  the  other  with  a  cork  and  a  con- 
denser. When  ready,  the  receptacle  was  filled  with  Lake  Michigan  water 
and  a  Bunsen  burner  was  placed  so  as  to  heat  the  sandstone  cylinder  within 
the  iron  tube.  One  side  of  the  sandstone  was  thus  kept  at  a  temperature 
slightly  above  100°,  while  the  other  face,  in  contact  with  the  water,  remained 
just  at  the  boiling-point.  Water  was  found  to  penetrate  the  porous  cylinder 
readily,  evaporating  and  leaving  its  dissolved  material  within  the  mass 
of  the  sandstone,  and  escaping  as  steam  on  the  farther  side.  The  rate  at 
which  the  water  passed  through  the  sandstone  at  the  outset  was  not  deter- 
mined, but  after  5  liters  of  lake  water  had  been  used,  it  was  found  that 
129  cubic  centimeters  traversed  the  rock  and  were  condensed  in  one  hour. 
The  rate  slowly  fell  as  the  experiment  progressed.  While  the  thirteenth 
liter  was  being  used,  only  73  cubic  centimeters  passed  through  the  sand- 
stone per  hour.  It  was  evident  that  the  pores  were  becoming  clogged, 
but  to  complete  the  experiment  with  Lake  Michigan  water,  which  contains 
only  150  parts  of  solid  matter  per  million,  would  have  required  too  much 
time.  To  hasten  the  process,  a  saturated  solution  of  calcium  sulphate 
was  substituted.  This  soon  caused  a  marked  slackening  of  the  passage  of 
water  through  the  rock,  and  doubtless  would  have  sealed  the  pores  com- 
pletely, if  allowed  sufficient  time. 

From  this  experiment,  it  appears  certain  that  water,  evaporating  in 
the  pore  spaces  of  a  rock  and  escaping  as  steam,  will  leave  behind  what- 
ever material  is  in  solution,  until  the  crevices  become  clogged  and  the 
penetration  of  water  ceases.  This  principle  may  be  applied  to  the  outer 
6,900  feet  of  the  earth's  crust;  in  the  superficial  portion  of  this  zone  it 
should  be  very  effective,  since  the  conditions  more  nearly  approach  those 
of  the  experiment;  in  the  lower  portion  of  this  belt,  as  6,900  feet  and  the 
critical  pressure  (as  well  as  temperature  in  the  neighborhood  of  hot  volcanic 
pipes)  is  approached,  the  density,  and  hence  the  solvent  powers,  of  the 
water-vapor  approach  those  of  the  liquid.  The  vapor,  also,  should  escape 
less  readily  from  the  liquid  at  these  depths,  since  the  expansive  force  of 
the  vapor  drives  the  water  back  along  its  path  with  more  difficulty.  Toward 
the  critical  point  of  water,  therefore,  the  application  of  this  principle 
becomes  more  uncertain,  but  it  would  seem  to  be  operative  also  at  these 
depths,  though  more  and  more  slowly  as  the  critical  point  is  neared. 

It  might  be  objected  that  the  passage  of  water  into  vapor,  involving 
the  latent  heat  of  steam,  would  keep  the  adjacent  rocks  cool  and  cause  the 
deposition  to  take  place  at  the  very  contact  where  the  hot  lava  could  fuse, 
and  dissolve,  the  precipitated  salts.  But  it  is  very  doubtful  whether  the 
vaporization  of  such  a  small  quantity  of  water,  taking  place  with  the  slow- 
ness imposed  upon  it  by  the  minuteness  of  the  capillary  pores,  would  keep 
the  contact  rocks  at  a  temperature  below  365°.  The  gap  between  365° 
and  1100°  is  too  great  for  there  not  to  be  a  space,  if  of  a  few  inches  only, 
at  an  intermediate  temperature.  It  is  also  to  be  remembered  that  the 
latent  heat  of  steam  diminishes  with  the  pressure  until,  at  the  critical 
point,  it  becomes  zero.  The  testimony  of  the  country  rocks  through 
which  a  volcanic  conduit  has  passed  is  that  metamorphism  has  usually 
progressed  to  some  distance  from  the  contact  of  igneous  intrusion.  In  a 
long-established  volcano,  where  the  rocks  surrounding  the  conduit  have 


VULCANISM.  73 

been  heated  to  high  temperatures,  the  deposition  of  the  solutes  from  any 
penetrating  water  should  have  sealed  the  capillary  tubes  and  fissures  at 
a  distance  from  the  lava  such  that  the  latter  cannot  absorb  them  and 
keep  the  water-way  open.  Kemp  has  stated  in  a  recent  paper  *  that  at  the 
contacts  with  eruptives,  limestone  rocks,  instead  of  being  porous,  are 
prevailingly  dense  and  compact,  and  often  very  hard  to  drill,  as  if  due  to 
deposition  within  their  interstices.  However,  the  author  assigned  this 
supposed  deposition  to  magmatic  waters  from  the  intrusion.  This  brings 
up  a  widely  established  view  that  magmas,  instead  of  absorbing  water  from 
the  intruded  rocks,  give  it  off,  depositing  matter  in  solution  to  form  veins  in 
the  zone  of  fracture. 
To  quote  Van  Hise : 2 

In  the  belt  of  cementation,  in  consequence  of  the  porosity  of  that  zone,  the  material 
of  the  magma,  both  by  direct  injection  and  by  transmission  through  water,  may  pro- 
foundly affect  the  average  chemical  composition  of  the  intruded  rock  for  great  distances 
from  the  intrusive  mass. 

Geikie  cites  a  case  in  Bohemia,  where  certain  Senonian  marls,  invaded 
by  a  mass  of  Tertiary  dolerite,  begin  to  get  darker  in  color  and  harder 
in  texture  at  a  distance  of  800  meters  from  the  contact,  while,  as  the  intru- 
sive mass  is  approached,  the  interstratified  beds  of  sandstone  have  been 
indurated  to  the  compactness  of  quartzite.3 

But  considering  only  meteoric  waters  at  depths  greater  than  6,900 
feet,  where  water  remains  liquid  up  to  the  critical  temperature,  it  is  less 
probable  that  the  pore  spaces  will  be  filled  up  in  this  manner.  Nor  does 
it  seem  likely  that  DaubreVs  theory  that  water  may  penetrate  rocks 
against  a  steam-pressure  can  operate  at  these  depths,  since  that  principle 
is  dependent  upon  a  marked  difference  between  the  capillarity  of  water 
and  of  steam,  while  at  the  critical  point,  the  density  of  water-gas  being 
the  same  as  that  of  water,  this  force  should  be  absent.  The  problem  then 
becomes  a  question  of  equilibrium  between  the  hydrostatic  column  of 
water  and  that  of  the  lava,  in  which  the  pressure  of  the  lava  at  a  depth  of 
7,000  feet  should  be  in  the  neighborhood  of  2.7  times  that  of  the  water, 
though  this  preponderance  steadily  diminishes  as  the  water-gas  becomes 
condensed,  with  increasing  depth,  at  a  rate  higher  than  lava.  Whether 
under  these  conditions  lava  can  absorb  water-gas,  is  an  open  question. 

Water  can  only  penetrate  from  25,000  to  30,000  feet  below  the  surface 
on  account  of  the  closure  of  all  crevices  by  pressure.  But  on  the  assumption 
that  the  temperature  gradient  in  the  outer  part  of  the  earth's  crust  is  1°  C. 
for  each  100  feet  of  descent  (which  is  probably  too  high)  the  critical  tem- 
perature will  not  be  reached,  except  in  the  neighborhood  of  volcanic  intru- 
sions, until  at  a  depth  of  about  36,000  feet.  Hence,  over  the  greater  part 
of  the  earth,  water  will  remain  in  the  liquid  state  as  far  down  as  fractures 
and  fissures  will  allow  it  to  seep,  and  no  appeal  can  be  made  to  the  more 
rapid  and  potent  gaseous  diffusion  to  carry  it  beyond  30,000  feet.  But 
because  of  their  heat,  lavas  must  originate  at  much  greater  depths  below 
the  surface,  and  hence  far  beyond  the  reach  of  surface-waters,  which  can 

1  Kemp,  Economic  Geol.,  vol.  2,  p.  11. 

1  Van  Hise,  Monograph  47,  U.  S.  G.  S.,  p.  714. 

8  Hibsch,  cited  by  Geikie,  Textbook  of  Geology,  vol.  2,  p.  774. 


74  THE    GASES   IN   ROCKS. 

only  come  in  contact  with  them,  and  only  doubtfully  then,  in  a  very  limited 
portion  of  the  throat  of  the  volcano. 

These  considerations  seem  to  indicate  that,  for  the  most  part,  the  volcanic 
gases  and  vapors  have  not  been  supplied  to  the  lavas  by  ground  waters, 
but  are  original  constituents  of  the  magmas.  Doubtless  at  the  beginning 
of  an  eruption,  following  a  period  of  quiescence,  much  of  the  steam  merely 
comes  from  such  rain-water  as  may  have  accumulated  in  the  crater  and 
upper  part  of  the  cone,  but  this  does  not  account  for  the  gaseous  emanations 
from  the  lava  itself,  nor  from  those  volcanoes,  such  as  Stromboli,  and  the 
well-known  Solfatara  near  Naples,  which  maintain  a  mild  form  of  eruption 
for  long  periods.  Such  meteoric  water  could  contribute  to  the  volcanic  gases 
little  except  some  dissolved  air,  together  with  a  trace  of  carbon  dioxide, 
and  perhaps  hydrogen  from  chemical  action.  Such  soluble  salts  as  this 
water  might  dissolve  from  the  crater  walls  were  brought  up  from  the  in- 
terior in  the  first  place  (making  some  allowance,  however,  for  weathering), 
and  so  have  little  bearing  on  the  case. 

The  hypothesis  that  the  gases  and  vapors  are  originally  from  the  mag- 
mas, is  greatly  strengthened  by  the  volcanic  activity  in  the  moon,  if,  as 
is  rather  generally  believed,  the  great  pits  on  the  surface  of  the  moon  are 
craters  produced  by  volcanic  explosions;  if  not,  of  course  the  argument 
does  not  hold.  The  gases  and  vapors  which  caused  the  tremendous  out- 
bursts can  not  be  ascribed  to  the  penetration  of  surface-waters  and  gases, 
for  the  moon  has  neither  appreciable  atmosphere  nor  hydrosphere,  and, 
according  to  Stoney's  doctrine,  never  could  have  held  either,  owing  to  its 
feeble  gravitative  control.  Such  gases  as  are  implied  by  these  explosions 
must  be  supposed  to  have  arisen  from  within  the  interior  of  the  moon. 
The  extent  of  this  explosive  lunar  vulcanism,  in  the  absence  of  any  appre- 
ciable atmosphere  or  hydrosphere,  furnishes  a  strong  argument  against 
the  belief  that  surface-waters  and  atmospheric  gases  are  essential  factors 
in  terrestrial  vulcanism. 

Thus  far  evidence  of  a  negative  nature  has  been  brought  forward  to 
show  the  difficulties  in  the  way  of  thinking  that  surface-waters  play  a 
prominent  r61e  in  volcanic  phenomena.  But  more  positive  evidence  can 
be  presented  to  support  the  view  that  the  hydrogen  and  water  in  the  deep- 
seated  rocks  are  truly  magmatic.  Micas  are  prominent  constituents  of  the 
plutonic  rocks.  The  immense  granitic  bathyliths,  which  were  probably 
formed  beyond  the  reach  of  ground-waters,  are  characterized  by  this  group 
of  minerals.  In  fact,  micas  are  more  abundant  in  the  deep-seated  rocks 
than  in  the  surface  lavas  of  similar  composition.  Yet  all  micas  contain 
hydrogen  (or  hydroxyl)  and  yield  water  upon  ignition.  This  varies  with 
the  mineral  species  and  locality,  ranging  up  to  4  or  5  per  cent.  If  these 
micas  in  the  massive  intrusions  are  primary  minerals,  as  they  seem  to  be, 
and  were  out  of  the  reach  of  ground- waters  until  long  after  they  were  crys- 
tallized, there  appears  no  other  alternative  than  to  consider  this  hydrogen 
as  inherent  in  the  magma  itself.  The  general  petrological  principle  that 
plutonic  rocks  are  micaceous  and  hornblendic,  while  their  more  superficial 
equivalents  are  more  frequently  characterized  by  pyroxenes  which  are 
less  hydrous,  may  point  toward  the  suggestion  that  the  magmas  originally 
contain  considerable  water  or  the  elements  which  can  produce  it,  but  as 


VULCANISM.  75 

they  approach  the  surface  much  of  the  hydrogen  and  water-vapor  escapes 
and  pyroxene  minerals  crystallize  instead  of  these  hydrous  micas. 

All  of  these  facts  and  deductions  lead  to  the  general  conclusion  that 
our  surface-waters  have  been  derived  from  the  interior  of  the  earth,  and 
oppose  the  idea  that  to  explain  the  presence  of  hydrogen,  or  water,  in 
magmas  and  rocks,  we  have  merely  to  appeal  to  the  penetration  of  surface- 
waters.  The  meteoric  waters  are  limited  to  their  superficial  place  and 
function,  both  in  the  evolution  of  magmas  and  in  vulcanism;  an  ultimate 
source  is  found  for  these  waters;  and  a  steady  supply  of  water  and  gases 
is  furnished  to  the  earth  to  offset  the  loss  of  vapor  into  space,  and  thus 
contributes  to  the  globe  one  of  the  factors  necessary  to  a  long  period  of 
habitability  for  living  organisms. 

VOLCANIC   GASES. 

The  gases  which  escape  from  fumarolic  vents  are  in  many  respects 
similar  to  those  obtained  by  heating  igneous  rocks  in  vacuo,  but  with  the 
addition  of  oxygen  and  vapors  of  chlorides,  fluorides,  boric  acid,  and  other 
high-temperature  volatilizations.  Though  nitrogen  is  much  more  con- 
spicuous in  the  analyses  of  volcanic  gases  than  in  those  from  rocks,  this  is 
doubtless  due,  in  the  main,  to  a  mixture  with  atmospheric  air.  However, 
the  greater  heat  of  the  volcano  would  also  favor  a  higher  proportion  of 
nitrogen,  as  shown  by  my  experiment.  Much  of  the  oxygen  also  is  probably 
from  the  air.  But  an  analysis  of  gas  escaping  from  a  stream  of  lava 
flowing  on  the  sea  bottom  at  Santorin  gave  Fouqu6:  oxygen,  21.11  per 
cent;  nitrogen,  21.90  per  cent;  and  hydrogen,  56.70  per  cent.1  This  would 
suggest  that  the  dissociation  of  water  also  contributes  free  oxygen. 

Fouque"'s  studies  at  Santorin  confirm  the  law  of  variation  in  composi- 
tion of  volcanic  gases,  first  established  by  Sainte-Claire  Deville,2  namely, 
that  the  nature  of  the  gas  evolved  depends  upon  the  phase  of  volcanic 
activity.  Hydrochloric  acid,  with  free  chlorine  and  fluorine,  is  given  off 
only  from  the  hottest  fumaroles  where  the  heat  is  sufficient  to  liberate 
these  gases  from  chlorides  and  fluorides.  At  less  active  vents,  sulphur 
dioxide  is  the  most  noticeable  of  the  corrosive  gases,  while  the  cooler  fuma- 
roles exhale  chiefly  hydrogen  sulphide,  carbon  dioxide,  and  nitrogen. 
Carbon  dioxide  and  nitrogen  escape  from  all  the  fumaroles.  Fouque" 
found  that  the  relative  importance  of  hydrogen  increased  with  rise  of 
temperature,  and  that  his  marsh-gas  (which,  owing  to  an  imperfection  in 
the  method  of  analysis  in  1867,  may  have  been  carbon  monoxide,  or  a 
mixture  of  carbon  monoxide  and  marsh-gas)  diminished  as  the  activity 
increased.  These  observations  are  entirely  in  accord  with  the  results  of 
my  differential  temperature  experiments  with  rock  powders.  Hydrogen 
sulphide  and  carbon  dioxide  are  the  gases  expelled  from  the  rocks  at  the 
lowest  temperatures;  carbon  monoxide  and  marsh-gas  appear  at  inter- 
mediate temperatures,  while  hydrogen  is  most  prominent  when  the  heat 
is  carried  to  bright  redness.  Nitrogen  is  most  abundantly  liberated  at  red 
heat;  hence  the  presence  of  that  gas  at  the  cooler  vents  and  fissures  is 
chiefly  due  to  atmospheric  air. 

1  Fouque"  Santorin  et  sea  Eruptions,  p.  230. 

2  Sainte-Claire  Deville,  Ann.  de  Chim.  et  Phys.,  52  (1858),  p.  60. 


76  THE    GASES    IN   ROCKS. 

While  carbon  dioxide  escapes  from  all  fumaroles  in  greater  or  less 
degree,  it  is  at  those  vents  whose  activity  has  subsided  beyond  the  point 
where  hydrogen  and  the  noxious  gases  are  evolved  that  this  gas  is  most 
conspicuous.  For  this  reason,  carbon  dioxide  has  come  to  be  regarded  as 
marking  the  dying  of  the  volcanic  activity.  A  source  for  carbon  dioxide 
after  the  disappearance  of  the  other  gases  has  been  sought  in  the  neigh- 
boring limestone  formations,  either  from  baking  or  from  the  chemical 
action  of  halogen  or  sulphur  acids.  The  obvious  difficulty  confronting 
this  conception  is  that  limestone  is  not  always  present  to  furnish  carbon 
dioxide.  Experiments  show  that  below  400°  C.  carbon  dioxide  is  the 
principal  gas  evolved  from  rock  material,  and  as  the  lava  solidifying  in 
the  crater,  or  conduit,  has  not  lost  all  its  gas,  it  is  only  a  part  of  the  natural 
sequence  of  events  that  the  escape  of  carbonic  anhydride  from  the  cooling 
lavas  should  continue  for  some  time  after  the  volcano  has  settled  into 
quiescence.  Some  of  this  carbon  dioxide  doubtless  also  comes  from  previ- 
ous lavas  which,  warmed  again  by  the  fresh  lava,  give  up  some  of  the  carbon 
dioxide  which  my  experiments  show  them  to  contain. 

AMMONIUM    CHLORIDE    DEPOSITS. 

Among  the  various  substances  which  are  deposited  around  fumaroles, 
sal-ammoniac,  or  ammonium  chloride,  is,  in  some  respects,  one  of  the  most 
remarkable.  Compounds  of  ammonium  have  not  yet  been  recognized  in 
igneous  rocks,  although  rock  powders  often  give  off  small  quantities  of 
ammonia  gas  when  heated  in  vacuo.  Chemical  analyses  of  spring- waters 
report  ammonium  salts  only  in  traces,  such  as  may  have  been  derived 
from  the  decay  of  organic  matter.  If  ground- waters  be,  for  the  most  part, 
unable  to  reach  the  lavas,  even  this  rather  doubtful  source  of  ammonium 
compounds  is  not  available.  If  the  elements  of  the  radical  NH4  be  supposed 
to  have  come  from  the  interior  magma,  there  are  two  alternative  hypotheses 
still  open.  The  first  assumes  that  the  radical  NH4  existed  intact  in  the 
magmatic  solution  in  the  form  of  ammonium  salts  and,  volatilized  by  the 
heat  upon  the  relief  of  pressure,  gradually  collected  on  the  cooler  portions 
of  the  crater.  This  hypothesis  must,  however,  explain  the  apparent  absence 
of  these  compounds  in  igneous  rocks.  The  second  believes  that  the  am- 
monium chloride  was  formed  synthetically  in  the  throat  of  the  volcano, 
from  the  nitrogen,  hydrogen,  and  hydrochloric-acid  gases.  This  would  make 
it  a  direct  product  of  volcanic  gases. 

The  presence  of  ammonia,  or  its  vaporized  salts,  in  volcanic  emana- 
tions leads  to  the  formation  of  another  interesting  compound.  Silvestri  * 
has  found  iron  nitride,  as  a  lustrous  metallic  deposit,  at  a  fumarole  on 
Etna.  This  compound  is  due  either  to  a  reaction  between  the  sublimed 
ferric  chloride  and  free  ammonia  gas  or  to  the  ignition  of  the  iron-bearing 
lava  in  the  presence  of  ammonium  chloride  vapor.  The  appearance  of  iron 
nitride  around  fumaroles  throws  no  direct  light  upon  the  question  of  its 
existence  in  the  magmas,  though  it  indirectly  leads  to  the  hypothesis  that 
the  nitrogen  in  the  ammonia  and  its  compounds  came  originally  from  iron 
nitride  within  the  magma. 

1  Silvestri,  Pogg.  Ann.,  vol.  157  (1876),  pp.  165-172. 


SUBTERRANEAN    GASES.  77 

SUBTERRANEAN  GASES. 

The  atmosphere  is  now  being  fed  by  gases  which  escape  through  out- 
lets other  than  those  of  active  volcanoes.  Work  in  the  shafts  of  many 
deep  mines  in  different  parts  of  the  world  is  often  impeded  by  the  exhala- 
tion of  gases  from  the  rocks.  This  is,  of  course,  familiar  in  the  case  of 
organic  rocks,  such  as  coal,  in  which  the  decomposition  of  organic  substances 
is  in  progress.  Reference  is  here  made  especially  to  gases  escaping  from 
crystalline  or  other  inorganic  rocks.  An  exhalation  of  this  kind  is  a 
notable  phenomenon  in  several  of  the  mines  in  the  Cripple  Creek  region  of 
Colorado,  where  nitrogen  and  carbon  dioxide  are  poured  into  the  workings 
in  considerable  quantities  when  the  barometer  is  low.1  Two  analyses  of  the 
gas  escaping  into  the  Conundrum  mine  at  Cripple  Creek  gave  the  following : 

1st:  Carbon  dioxide,  10.2;  oxygen,  5.7;  nitrogen,  84.1;  total,  100. 

2d:  Carbon  dioxide,  8.3;  oxygen,  10.2;  nitrogen,  81.5;  total,  100. 

No  carbon  monoxide,  marsh-gas,  or  hydrocarbons  were  detected. 

The  gas  from  the  Elkton  mine,  which  was  analyzed  by  Dr.  A.  W.  Browne, 
of  Cornell  University,  consisted  of  nearly  the  same  gases  as  from  the  Con- 
undrum mine:  Water-vapor,  1.4;  carbon  dioxide,  14.7;  oxygen,  5.6;  nitro- 
gen, 76.8;  argon,  1.5;  total,  100.0.  Hydrocarbons,  methane,  and  hydrogen 
were  absent.2  The  authors  estimate  that  this  gas  may  be  considered  to  be 
25  per  cent  of  air,  59  per  cent  of  nitrogen  and  argon,  15  per  cent  of  carbon 
dioxide,  and  1  per  cent  of  water-vapor.  The  gas  apparently  is  derived 
from  greater  depths  than  those  at  which  it  issues,  since  it  is  warmer  than  the 
air  of  the  mines,  and  since  practically  no  gas  was  encountered  in  the  oxidized 
zone.  They  regard  the  outpouring  as  the  last  exhalation  of  the  extinct 
volcano,  around  whose  neck  the  Cripple  Creek  mines  are  located. 

In  some  of  the  potash  mines  in  the  vicinity  of  Strassf  urt  trouble  is  caused 
by  the  escape  of  combustible  gas  into  the  workings.  According  to  Precht,3 
blowers  of  this  gas  once  lighted  have  burned  continuously  for  periods  as  long 
as  two  months.  An  analysis  of  this  gas  by  Precht  shows  it  to  be  largely 
hydrogen.  His  figures  are:  Hydrogen,  93.05;  methane,  0.778;  carbon  dioxide, 
0.180;  carbon  monoxide,  trace;  oxygen,  0.185;  nitrogen,  5.804;  total,  100.002. 
This  investigator  believed  that  but  little  of  the  hydrogen  could  have  come 
from  the  decomposition  of  organic  matter;  instead,  he  sought  a  source  for  it 
in  the  possible  oxidation  of  ferrous  chloride  in  the  salt  by  water,  according 
to  the  reaction: 

6FeCl2  -f  3H2O  =  2Fe2Cl8 + Fe2Os  +  3H3 

This  source  of  hydrogen  is  somewhat  analogous  to  the  production  of  the 
same  gas  by  the  action  of  water  upon  ferrous  compounds  at  high  tempera- 
tures, which  has  already  been  discussed,  except  that  in  the  salt  beds  the 
supposed  action  has  taken  place  at  the  ordinary  underground  temperature. 
But  these  gases  coming  from  the  sedimentary  salt  beds  of  the  Upper  Per- 
mian represent,  of  course,  gas  merely  restored  to  the  atmosphere,  and  not 
an  original  contribution  to  it. 

1  Lindgren  and  Ransome,  Prof.  Paper  54,  U.  S.  G.  S.,  pp.  252-270.  *  Loc.  tit. 

3  H.  Precht,  Ber.  Deutech.  Chem.  Gesell.,  vol.  12  (1879),  pp.  557-561. 


78  THE    GASES   IN    ROCKS. 

Nitrogen  with  an  abnormal  amount  of  inert  gas  (probably  both  argon 
and  helium)  occurs,  under  high  pressure,  in  a  gas-well  at  Dexter,  Kansas.1 
However,  instead  of  being  derived  from  igneous  rocks,  this  comes  from  a 
gas-bearing  sand  near  the  contact  of  the  Permian  with  the  Upper  Carbonif- 
erous. An  analysis  of  this  gas  gave:2  Oxygen,  0.20;  methane,  15.02; 
hydrogen,  0.80;  nitrogen,  71.89;  inert  residue,  12.09;  total,  100. 

Neither  carbon  dioxide  nor  carbon  monoxide  was  present  in  this  gas. 
The  methane,  and  perhaps  the  hydrogen  also,  may  be  attributed  to  the 
decomposition  of  organic  matter,  since  natural  gas-wells  exist  at  no  great 
distance  away.  But  the  remarkable  feature  of  this  analysis  is  the  large 
amount  of  nitrogen  with  the  very  abnormal  percentage  of  inert  gas. 
From  this  analysis,  and  the  testimony  of  many  spring-waters  which  give 
off  considerable  quantities  of  argon  and  helium,  it  would  appear  that 
gases  often  collect  underground  somewhat  in  proportion  to  their  chemical 
inertness.  The  chemically  active  gases  apparently  are  more  largely  retained 
within  the  rocks  by  combination,  while  nitrogen,  having  less  power  to 
unite  chemically,  more  largely  escapes  from  the  rocks  and  accumulates  in 
reservoirs.  Argon,  still  more  inert  than  nitrogen,  thus  may  reach  such  a 
high  proportion  as  12  per  cent. 

GENERAL  RELATIONS. 
RELATIVE  TO  THE  HYPOTHESIS  OF  A  MOLTEN  EARTH. 

These  studies  show  that,  within  the  range  of  temperature  employed, 
heat  causes  the  expulsion  of  gases  in  whatever  form  they  are  held,  and 
that  the  greater  the  degree  of  heat  the  more  quickly  and  completely  the 
gases  are  given  off.  There  is  reason  to  believe  that  this  principle  applies 
to  the  molten  state  as  well  as  to  the  solid  condition.  If  it  be  applicable 
to  liquid  lavas,  it  would  favor  the  belief  that  a  molten  globe  would  have 
boiled  out  most  of  its  gaseous  matter  before  solidifying.  Gases  near  the 
surface  should  escape  rapidly.  It  might,  perhaps,  on  first  thought,  be  held 
that,  while  much  of  the  gas  in  the  outer  portion  would  be  lost,  that  exist- 
ing in  the  central  part  of  the  sphere  would  be  retained  and  slowly  recharge 
the  peripheral  portion  after  a  crust  had  formed  and  prevented  further 
escape;  but  the  molten  globe,  by  hypothesis,  grew  up  gradually,  and  essen- 
tially every  part  was  once  superficial.  Even  to-day,  in  an  essentially  solid 
earth,  there  are  movements  of  lava  that  bring  up  gases  from  unknown 
depths,  and  it  is  reasonable  to  suppose  that  the  molten  sphere  was  stirred 
up  by  still  more  effective  convection  currents  which  facilitated  the  expulsion 
of  gases  and  vapors,  and  that  almost  all  of  the  gaseous  material  of  the 
globe  would  have  been  boiled  out  before  solidification  set  in. 

The  complete  validity  of  this  view  depends  much  upon  the  fate  of  the 
gases  after  they  have  reached  the  surface.  If  they  were  retained  in  the 
form  of  a  dense  atmosphere,  a  condition  of  pressure-equilibrium  might 
be  established  between  the  atmosphere  and  the  gases  in  the  liquid  earth, 
by  means  of  which  the  latter  would  retain  some  appreciable  amount  of 
gas.  But  if,  as  some  believe,  our  atmosphere  is  about  all  that  the  earth 

1  Haworth  and  McFarland,  Science,  vol.  21  (1905),  pp.  191-193.  2  Loc.  cit. 


GENERAL   RELATIONS.  79 

can  control,1  the  gas  expelled  from  the  molten  sphere  in  excess  of  the  mass 
of  the  present  atmosphere  would  escape  and  be  lost  to  the  planet.  Geo- 
logical evidences — early  Cambrian  glaciation,  Paleozoic  periods  of  aridity, 
and  the  general  testimony  of  life — all  point  toward  the  conclusion  that 
early  terrestrial  atmospheric  conditions  were  not  radically  different  from 
those  of  to-day.  If  the  hypothesis  of  a  heavy  atmosphere  be  not  permissi- 
ble, it  becomes  very  difficult  to  explain  the  presence  of  original  gases  and 
gas-producing  compounds  in  plutonic  rocks  on  the  basis  of  the  Laplacian 
or  other  hypotheses  that  postulate  original  fluidity. 

RELATIVE  TO  THE  PLANETESIMAL  HYPOTHESIS. 

After  the  gaseous  matter  of  the  ancestral  sun  was  shot  out  from  the 
solar  surface  to  form  the  two  arms  of  the  spiral  nebula,  as  postulated  by 
the  planetesimal  hypothesis,  the  rock-producing  portion  is  supposed  either 
to  have  aggregated  into  planetesimal  bodies,  or  to  have  been  gathered, 
molecule  by  molecule,  into  the  nucleus  of  the  earth.  The  planetesimal 
bodies  gathered  in  gas  molecules  of  the  atmospheric  class  both  by  chemical 
union  and  by  surface  adhesion  or  occlusion.  As  the  earth  grew  by  sweep- 
ing in  the  planetesimals,  whatever  gases  they  contained  became  entrapped 
in  the  body  of  the  growing  planet  and  well  distributed  throughout  its 
mass.  At  first,  the  gravity  of  the  earth  may  possibly  have  been  able  to 
hold  only  the  gases  brought  in  by  planetesimal  aggregates  of  rock  material 
and  those  that  became  impounded  in  it  by  impact,  but  at  a  later  stage, 
when  increased  mass  enabled  it  to  hold  gaseous  molecules,  gases  may  have 
been  added  to  the  atmosphere  directly  from  the  nebula,  and  these,  by 
chemical  reactions,  may  have  become  united  with  the  surface  rocks.  As 
soon  as  vulcanism  commenced,  a  system  of  exchange  was  set  up.  While 
gases  were  being  fed  to  the  atmosphere  by  volcanic  action,  water,  carbon 
dioxide,  oxygen,  and  nitrogen  were  being  buried  with  the  surface  rock 
material,  partly  by  chemical  union  and  partly  by  mechanical  entrapment, 
as  the  growth  by  infalling  matter  continued.  It  is  thus  quite  easy  to 
understand  how  the  earth  came  to  be  affected  by  these  gases  throughout 
its  mass,  and  how  they  came  to  exist  there  in  all  available  forms  of  retention. 

While  the  carbon  monoxide  and  methane  derived  from  rocks  by  heat- 
ing in  vacuo  are  doubtless  chiefly  produced  from  the  carbon  dioxide  and 
water  present  in  the  rock  material,  there  seems  good  reason  to  suppose 
that  similar  reactions  took  place  within  the  earth,  as  the  surface  material 
became  buried  and  heated,  and  hence  that  carbon  monoxide  and  methane 
exist,  as  such,  in  the  earth's  body,  and  are  to  be  reckoned  among  the  natural 
gases  of  the  rocks. 

RELATIVE  TO  ATMOSPHERIC  SUPPLY. 

The  fact  that  many  of  the  igneous  rocks  are  able  to  yield  hydrogen 
from  reactions  between  water  and  ferrous  compounds,  at  high  tempera- 
tures, indicates  that  the  material  of  the  earth's  crust  is  in  a  condition  of 
partial  oxidation  only.  Near  the  center  of  the  earth  there  is  probably 
very  little  oxygen,  and  even  up  to  the  "surface,  barring  the  weathered 

>  R.  H.  McKee,  Science,  vol.  23  (1906),  pp.  271-274. 


80  THE    GASES   IN    ROCKS. 

mantle,  the  rocks  are  suboxidized.  Yet  the  earth  is  surrounded  by  an 
oxygenated  atmosphere.  Since  oxygen  is  not  developed  in  the  combustion- 
tube,  and  does  not  appear  to  exist  as  a  free  gas  in  igneous  rocks,  it  is  not 
likely  that  this  constituent  of  the  atmosphere  has  come  directly  as  an 
exudation  from  the  interior  of  the  globe.  It  is  to  be  sought,  rather,  in  a 
dissociation  or  decomposition  of  compound  gases  by  physical  or  organic 
agencies.  Originally,  enough  oxygen  was  derived  from  water-vapor,  by 
physical  means,  to  permit  the  beginning  of  plant  life;  after  vegetation  ap- 
peared, an  abundant  source  of  oxygen  was  found  in  the  carbon  dioxide. 

The  average  gas  content  of  igneous  rocks,  as  determined  by  the  analyses 
now  made,  may  be  used  to  test  the  competence  of  the  rocks  to  yield  the 
present  atmosphere.  Taking  the  average  volume  of  nitrogen  per  volume 
of  rock  to  be  0.05,  which  is  probably  nearer  the  truth  than  the  figure  0.09 
given  in  table  16  *  (owing  to  leakage  of  air),  it  would  require  the  liberation 
of  all  the  nitrogen  in  the  outermost  70  miles  of  the  earth's  crust  to  produce 
the  nitrogen  in  the  present  atmosphere.  For  an  estimate  of  the  amount 
of  igneous  rock  necessary  to  yield  the  carbon  dioxide  which  is  now  locked 
up  in  limestone  and  coal  deposits,  we  may  take  Dana's  figure  of  50  atmo- 
spheres of  this  gas,  and  an  average  of  2.16  volumes  of  carbon  dioxide  per 
volume  of  rock.  To  produce  these  50  atmospheres  of  carbon  dioxide,  it 
is  found  that  a  thickness  of  66  miles  of  crust  would  have  to  be  deprived 
of  its  carbon  dioxide  2 — a  figure  which  corresponds  fairly  well  with  the 
estimate  for  nitrogen.  If  the  water  of  the  rocks  be  placed  at  2.3  per  cent, 
a  depth  of  70  miles  would  supply  the  hydrosphere. 

On  the  planetesimal  hypothesis,  gas  has  been  supplied  from  the  interior 
to  the  atmosphere  ever  since  an  early  stage  of  the  earth's  growth,  prob- 
ably from  the  earliest  stage  at  which  an  atmosphere  could  be  held,  which 
may  be  placed  at  the  time  when  the  earth's  radius  was  about  2,000  miles. 
From  this  it  appears  that  only  a  small  fraction  of  the  full  gas-producing 
possibilities  of  the  rocks  of  the  earth  was  required  to  supply  the  atmo- 
sphere. The  fact  that  gases  are  still  being  given  forth  through  volcanoes, 
and  that  the  ejected  lavas  still  have  gas-producing  qualities,  makes  it  clear 
that  all  the  resources  of  the  interior  are  not  yet  exhausted.  The  working 
qualities  of  the  planetesimal  hypothesis,  therefore,  do  not  seem  to  be  found 
wanting  in  either  past  possibilities  of  supply,  present  output,  or  prospective 


ACKNOWLEDGMENTS. 

In  conclusion,  I  wish  to  express  my  special  thanks  to  Dr.  Julius  Stieglitz 
for  constant  advice  in  the  conduct  of  the  chemical  researches;  to  Dr.  Oskar 
Eckstein  for  much  valuable  assistance  in  the  laboratory;  to  Dr.  R.  A. 
Millikan  for  helpful  suggestions  pertaining  to  physical  principles  and  the 
designing  of  new  pieces  of  apparatus;  and  to  my  father,  Dr.  T.  C.  Cham- 
berlin,  for  proposing  the  investigation,  and  for  constant  sympathy  and 
criticism  during  the  progress  of  the  work. 

1  Ante,  p.  28.  *  The  limestones,  of  course,  are  not  here  included. 


D -13744 
5-13 


DATE  DUE 


UC  SOUTHERN  REGIONAL  LIBRARY FACUJTY 


